Research-Methodology

Literature review sources

Sources for literature review can be divided into three categories as illustrated in table below. In your dissertation you will need to use all three categories of literature review sources:

Sources for literature review and examples

Generally, your literature review should integrate a wide range of sources such as:

  • Books . Textbooks remain as the most important source to find models and theories related to the research area. Research the most respected authorities in your selected research area and find the latest editions of books authored by them. For example, in the area of marketing the most notable authors include Philip Kotler, Seth Godin, Malcolm Gladwell, Emanuel Rosen and others.
  • Magazines . Industry-specific magazines are usually rich in scholarly articles and they can be effective source to learn about the latest trends and developments in the research area. Reading industry magazines can be the most enjoyable part of the literature review, assuming that your selected research area represents an area of your personal and professional interests, which should be the case anyways.
  • Newspapers can be referred to as the main source of up-to-date news about the latest events related to the research area. However, the proportion of the use of newspapers in literature review is recommended to be less compared to alternative sources of secondary data such as books and magazines. This is due to the fact that newspaper articles mainly lack depth of analyses and discussions.
  • Online articles . You can find online versions of all of the above sources. However, note that the levels of reliability of online articles can be highly compromised depending on the source due to the high levels of ease with which articles can be published online. Opinions offered in a wide range of online discussion blogs cannot be usually used in literature review. Similarly, dissertation assessors are not keen to appreciate references to a wide range of blogs, unless articles in these blogs are authored by respected authorities in the research area.

Your secondary data sources may comprise certain amount of grey literature as well. The term grey literature refers to type of literature produced by government, academics, business and industry in print and electronic formats, which is not controlled by commercial publishers. It is called ‘grey’ because the status of the information in grey literature is not certain. In other words, any publication that has not been peer reviewed for publication is grey literature.

The necessity to use grey literature arises when there is no enough peer reviewed publications are available for the subject of your study.

Literature review sources

John Dudovskiy

  • Subject guides
  • Researching for your literature review
  • Literature sources

Researching for your literature review: Literature sources

  • Literature reviews
  • Before you start
  • Develop a search strategy
  • Keyword search activity
  • Subject search activity
  • Combined keyword and subject searching
  • Online tutorials
  • Apply search limits
  • Run a search in different databases
  • Supplementary searching
  • Save your searches
  • Manage results

Scholarly databases

It's important to make a considered decision as to where to search for your review of the literature. It's uncommon for a disciplinary area to be covered by a single publisher, so searching a single publisher platform or database is unlikely to give you sufficient coverage of studies for a review. A good quality literature review involves searching a number of databases individually.

The most common method is to search a combination of large inter-disciplinary databases such as Scopus & Web of Science Core Collection, and some subject-specific databases (such as PsycInfo or EconLit etc.). The Library databases are an excellent place to start for sources of peer-reviewed journal articles.

Depending on disciplinary expectations, or the topic of our review, you may also need to consider sources or search methods other than database searching. There is general information below on searching grey literature. However, due to the wide varieties of grey literature available, you may need to spend some time investigating sources relevant for your specific need.

Grey literature

Grey literature is information which has been published informally or non-commercially (where the main purpose of the producing body is not commercial publishing) or remains unpublished. One example may be Government publications.

Grey literature may be included in a literature review to minimise publication bias . The quality of grey literature can vary greatly - some may be peer reviewed whereas some may not have been through a traditional editorial process.

See the Grey Literature guide for further information on finding and evaluating grey sources.

See the Moodle book MNHS: Systematically searching the grey literature for a comprehensive module on grey literature for systematic reviews.

In certain disciplines (such as physics) there can be a culture of preprints being made available prior to submissions to journals. There has also been a noticeable rise in preprints in medical and health areas in the wake of Covid-19.

If preprints are relevant for you, you can search preprint servers directly. A workaround might be to utilise a search engine such as Google Scholar to search specifically for preprints, as Google Scholar has timely coverage of most preprint servers including ArXiv, RePec, SSRN, BioRxiv, and MedRxiv.

Articles in Press are not preprints, but are accepted manuscripts that are not yet formally published. Articles in Press have been made available as an early access online version of a paper that may not yet have received its final formatting or an allocation of a volume/issue number. As well as being available on a journal's website, Articles in Press are available in databases such as Scopus and Web of Science, and so (unlike preprints) don't necessarily require a separate search.

Conference papers

Conference papers are typically published in conference proceedings (the collection of papers presented at a conference), and may be found on an organisation or Society's website, as a journal, or as a special issue of journal.

In certain disciplines (such as computer science), conference papers may be highly regarded as a form of scholarly communication; the conferences are highly selective, the papers are generally peer reviewed, and papers are published in proceedings affiliated with high-quality publishing houses.

Conference papers may be indexed in a range of scholarly databases. If you only want to see conference papers, database limits can be used to filter results, or try a specific index such as the examples below:

  • Conference proceedings citation index. Social science & humanities (CPCI-SSH)
  • Conference proceedings citation index. Science (CPCI-S)
  • ASME digital library conference proceedings

Honours students and postgraduates may request conference papers through Interlibrary Loans . However, conference paper requests may take longer than traditional article requests as they can be difficult to locate; they may have been only supplied to attendees or not formally published. Sometimes only the abstract is available.

If you are specifically looking for statistical data, try searching for the keyword statistics in a Google Advanced Search and limiting by a relevant site or domain. Below are some examples of sites, or you can try a domain such as .gov for government websites.

Statistical data can be found in the following selected sources:

  • Australian Bureau of Statistics
  • World Health Organization: Health Data and statistics
  • Higher Education Statistics
  • UNESCO Institute for Statistics
  • Tourism Australia Statistics

For a list of databases that include statistics see: Databases by Subject: Statistics .

If you are specifically looking for information found in newspapers, the library has a large collection of Australian and overseas newspapers, both current and historical.

To search the full-text of newspapers in electronic format use a database such as  Newsbank.

Alternatively, see the Newspapers subject guide for comprehensive information on newspaper sources available via Monash University library and open source databases, as well as searching tips, online videos and more.

Dissertations and theses

The Monash University Library Theses subject guide provides resources and guidelines for locating and accessing theses (dissertations) produced by Monash University as well as other universities in Australia and internationally.  

International theses:

There are a number of theses databases and repositories.

A popular source is:

  • ProQuest Dissertations & Theses Global  which predominantly, covers North American masters and doctoral theses. Full text is available for theses added since 1997. 

Australia and New Zealand theses:

Theses that are available in the library can be found using the  Search catalogue.

These include:

  • Monash doctoral, masters and a small number of honours theses 
  • other Australian and overseas theses that have been purchased for the collection.

Formats include print (not available for loan), microfiche and online (some may have access restrictions).

Trove includes doctoral, masters and some honours theses from all Australian and New Zealand universities, as well as theses awarded elsewhere but held by Australian institutions.

Tips:  

  • Type in the title, author surname and/or keywords. Then on the results page refine your search to 'thesis'.
  • Alternatively, use the Advanced search and include 'thesis' as a keyword or limi t your result to format = thesis
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Literature Reviews: Types of Literature

  • Library Basics
  • 1. Choose Your Topic
  • How to Find Books
  • Types of Clinical Study Designs

Types of Literature

  • 3. Search the Literature
  • 4. Read & Analyze the Literature
  • 5. Write the Review
  • Keeping Track of Information
  • Style Guides
  • Books, Tutorials & Examples

Different types of publications have different characteristics.

Primary Literature Primary sources means original studies, based on direct observation, use of statistical records, interviews, or experimental methods, of actual practices or the actual impact of practices or policies. They are authored by researchers, contains original research data, and are usually published in a peer-reviewed journal. Primary literature may also include conference papers, pre-prints, or preliminary reports. Also called empirical research .

Secondary Literature Secondary literature consists of interpretations and evaluations that are derived from or refer to the primary source literature. Examples include review articles (such as meta-analysis and systematic reviews) and reference works. Professionals within each discipline take the primary literature and synthesize, generalize, and integrate new research.

Tertiary Literature Tertiary literature consists of a distillation and collection of primary and secondary sources such as textbooks, encyclopedia articles, and guidebooks or handbooks. The purpose of tertiary literature is to provide an overview of key research findings and an introduction to principles and practices within the discipline.

Adapted from the Information Services Department of the Library of the Health Sciences-Chicago , University of Illinois at Chicago.

Types of Scientific Publications

These examples and descriptions of publication types will give you an idea of how to use various works and why you would want to write a particular kind of paper.

  • Scholarly article aka empirical article
  • Review article
  • Conference paper

Scholarly (aka empirical) article -- example

Empirical studies use data derived from observation or experiment. Original research papers (also called primary research articles) that describe empirical studies and their results are published in academic journals.  Articles that report empirical research contain different sections which relate to the steps of the scientific method.

      Abstract - The abstract provides a very brief summary of the research.

     Introduction - The introduction sets the research in a context, which provides a review of related research and develops the hypotheses for the research.

     Method - The method section describes how the research was conducted.

     Results - The results section describes the outcomes of the study.

     Discussion - The discussion section contains the interpretations and implications of the study.

     References - A references section lists the articles, books, and other material cited in the report.

Review article -- example

A review article summarizes a particular field of study and places the recent research in context. It provides an overview and is an excellent introduction to a subject area. The references used in a review article are helpful as they lead to more in-depth research.

Many databases have limits or filters to search for review articles. You can also search by keywords like review article, survey, overview, summary, etc.

Conference proceedings, abstracts and reports -- example

Conference proceedings, abstracts and reports are not usually peer-reviewed.  A conference article is similar to a scholarly article insofar as it is academic. Conference articles are published much more quickly than scholarly articles. You can find conference papers in many of the same places as scholarly articles.

How Do You Identify Empirical Articles?

To identify an article based on empirical research, look for the following characteristics:

     The article is published in a peer-reviewed journal .

     The article includes charts, graphs, or statistical analysis .

     The article is substantial in size , likely to be more than 5 pages long.

     The article contains the following parts (the exact terms may vary): abstract, introduction, method, results, discussion, references .

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  • Indian J Anaesth
  • v.60(9); 2016 Sep

Literature search for research planning and identification of research problem

Anju grewal.

Department of Anaesthesiology, Dayanand Medical College and Hospital, Ludhiana, Punjab, India

Hanish Kataria

1 Department of Surgery, Government Medical College and Hospital, Chandigarh, India

2 Department of Cardiac Anaesthesia, All India Institute of Medical Sciences, New Delhi, India

Literature search is a key step in performing good authentic research. It helps in formulating a research question and planning the study. The available published data are enormous; therefore, choosing the appropriate articles relevant to your study in question is an art. It can be time-consuming, tiring and can lead to disinterest or even abandonment of search in between if not carried out in a step-wise manner. Various databases are available for performing literature search. This article primarily stresses on how to formulate a research question, the various types and sources for literature search, which will help make your search specific and time-saving.

INTRODUCTION

Literature search is a systematic and well-organised search from the already published data to identify a breadth of good quality references on a specific topic.[ 1 ] The reasons for conducting literature search are numerous that include drawing information for making evidence-based guidelines, a step in the research method and as part of academic assessment.[ 2 ] However, the main purpose of a thorough literature search is to formulate a research question by evaluating the available literature with an eye on gaps still amenable to further research.

Research problem[ 3 ] is typically a topic of interest and of some familiarity to the researcher. It needs to be channelised by focussing on information yet to be explored. Once we have narrowed down the problem, seeking and analysing existing literature may further straighten out the research approach.

A research hypothesis[ 4 ] is a carefully created testimony of how you expect the research to proceed. It is one of the most important tools which aids to answer the research question. It should be apt containing necessary components, and raise a question that can be tested and investigated.

The literature search can be exhaustive and time-consuming, but there are some simple steps which can help you plan and manage the process. The most important are formulating the research questions and planning your search.

FORMULATING THE RESEARCH QUESTION

Literature search is done to identify appropriate methodology, design of the study; population sampled and sampling methods, methods of measuring concepts and techniques of analysis. It also helps in determining extraneous variables affecting the outcome and identifying faults or lacunae that could be avoided.

Formulating a well-focused question is a critical step for facilitating good clinical research.[ 5 ] There can be general questions or patient-oriented questions that arise from clinical issues. Patient-oriented questions can involve the effect of therapy or disease or examine advantage versus disadvantage for a group of patients.[ 6 ]

For example, we want to evaluate the effect of a particular drug (e.g., dexmedetomidine) for procedural sedation in day care surgery patients. While formulating a research question, one should consider certain criteria, referred as ‘FINER’ (F-Feasible, I-Interesting, N-Novel, E-Ethical, R-Relevant) criteria.[ 5 ] The idea should be interesting and relevant to clinical research. It should either confirm, refute or add information to already done research work. One should also keep in mind the patient population under study and the resources available in a given set up. Also the entire research process should conform to the ethical principles of research.

The patient or study population, intervention, comparison or control arm, primary outcome, timing of measurement of outcome (PICOT) is a well-known approach for framing a leading research question.[ 7 , 8 ] Dividing the questions into key components makes it easy and searchable. In this case scenario:

  • Patients (P) – What is the important group of patients? for example, day care surgery
  • Intervention (I) – What is the important intervention? for example, intravenous dexmedetomidine
  • Comparison (C) – What is the important intervention of comparison? for example, intravenous ketamine
  • Outcome (O) – What is the effect of intervention? for example, analgesic efficacy, procedural awareness, drug side effects
  • Time (T) – Time interval for measuring the outcome: Hourly for first 4 h then 4 hourly till 24 h post-procedure.

Multiple questions can be formulated from patient's problem and concern. A well-focused question should be chosen for research according to significance for patient interest and relevance to our knowledge. Good research questions address the lacunae in available literature with an aim to impact the clinical practice in a constructive manner. There are limited outcome research and relevant resources, for example, electronic database system, database and hospital information system in India. Even when these factors are available, data about existing resources is not widely accessible.[ 9 ]

TYPES OF MEDICAL LITERATURE

(Further details in chapter ‘Types of studies and research design’ in this issue).

Primary literature

Primary sources are the authentic publication of an expert's new evidence, conclusions and proposals (case reports, clinical trials, etc) and are usually published in a peer-reviewed journal. Preliminary reports, congress papers and preprints also constitute primary literature.[ 2 ]

Secondary literature

Secondary sources are systematic review articles or meta-analyses where material derived from primary source literature are infererred and evaluated.[ 2 ]

Tertiary literature

Tertiary literature consists of collections that compile information from primary or secondary literature (eg., reference books).[ 2 ]

METHODS OF LITERATURE SEARCH

There are various methods of literature search that are used alone or in combination [ Table 1 ]. For past few decades, searching the local as well as national library for books, journals, etc., was the usual practice and still physical literature exploration is an important component of any systematic review search process.[ 10 , 11 ] With the advancement of technology, the Internet is now the gateway to the maze of vast medical literature.[ 12 ] Conducting a literature review involves web-based search engines, i.e., Google, Google Scholar, etc., [ Table 2 ], or using various electronic research databases to identify materials that describe the research topic or those homologous to it.[ 13 , 14 ]

Methods of literature search

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Web based methods of literature search

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The various databases available for literature search include databases for original published articles in the journals [ Table 2 ] and evidence-based databases for integrated information available as systematic reviews and abstracts [ Table 3 ].[ 12 , 14 ] Most of these are not freely available to the individual user. PubMed ( http://www.ncbi.nlm.nih.gov/pubmed/ ) is the largest available resource since 1996; however, a large number of sources now provide free access to literature in the biomedical field.[ 15 ] More than 26 million citations from Medline, life science journals and online books are included in PubMed. Links to the full-text material are included in citations from PubMed Central and publisher web sites.[ 16 ] The choice of databases depends on the subject of interest and potential coverage by the different databases. Education Resources Information Centre is a free online digital library of education research and information sponsored by the Institute of Education Sciences of the U.S. Department of Education, available at http://eric.ed.gov/ . No one database can search all the medical literature. There is need to search several different databases. At a minimum, PubMed or Medline, Embase and the Cochrane central trials Registry need to be searched. When searching these databases, emphasis should be given to meta-analysis, systematic reviews randomised controlled trials and landmark studies.

Electronic source of Evidence-Based Database

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Time allocated to the search needs attention as exploring and selecting data are early steps in the research method and research conducted as part of academic assessment have narrow timeframes.[ 17 ] In Indian scenario, limited outcome research and accessibility to data leads to less thorough knowledge of nature of research problem. This results in the formulation of the inappropriate research question and increases the time to literature search.

TYPES OF SEARCH

Type of search can be described in different forms according to the subject of interest. It increases the chances of retrieving relevant information from a search.

Translating research question to keywords

This will provide results based on any of the words specified; hence, they are the cornerstone of an effective search. Synonyms/alternate terms should be considered to elicit further information, i.e., barbiturates in place of thiopentone. Spellings should also be taken into account, i.e., anesthesia in place of anaesthesia (American and British). Most databases use controlled word-stock to establish common search terms (or keywords). Some of these alternative keywords can be looked from database thesaurus.[ 4 ] Another strategy is combining keywords with Boolean operators. It is important to keep a note of keywords and methods used in exploring the literature as these will need to be described later in the design of search process.

‘Medical Subject Heading (MeSH) is the National Library of Medicine's controlled hierarchical vocabulary that is used for indexing articles in PubMed, with more specific terms organised underneath more general terms’.[ 17 ] This provides a reliable way to retrieve citations that use different terminology for identical ideas, as it indexes articles based on content. Two features of PubMed that can increase yield of specific articles are ‘Automatic term mapping’ and ‘automatic term explosion’.[ 4 ]

For example, if the search keyword is heart attack, this term will match with MeSH transcription table heading and then explode into various subheadings. This helps to construct the search by adding and selecting MeSH subheadings and families of MeSH by use of hyperlinks.[ 4 ]

We can set limits to a clinical trial for retrieving higher level of evidence (i.e., randomised controlled clinical trial). Furthermore, one can browse through the link entitled ‘Related Articles’. This PubMed feature searches for similar citations using an intricate algorithm that scans titles, abstracts and MeSH terms.[ 4 ]

Phrase search

This will provide pages with only the words typed in the phrase, in that exact order and with no words in between them.

Boolean operators

AND, OR and NOT are the three Boolean operators named after the mathematician George Boole.[ 18 ] Combining two words using ‘AND’ will fetch articles that mention both the words. Using ‘OR’ will widen the search and fetch more articles that mention either subject. While using the term ‘NOT’ to combine words will fetch articles containing the first word but not the second, thus narrowing the search.

Filters can also be used to refine the search, for example, article types, text availability, language, age, sex and journal categories.

Overall, the recommendations for methodology of literature search can be as below (Creswell)[ 19 ]

  • Identify keywords and use them to search articles from library and internet resources as described above
  • Search several databases to search articles related to your topic
  • Use thesaurus to identify terms to locate your articles
  • Find an article that is similar to your topic; then look at the terms used to describe it, and use them for your search
  • Use databases that provide full-text articles (free through academic libraries, Internet or for a fee) as much as possible so that you can save time searching for your articles
  • If you are examining a topic for the first time and unaware of the research on it, start with broad syntheses of the literature, such as overviews, summaries of the literature on your topic or review articles
  • Start with the most recent issues of the journals, and look for studies about your topic and then work backward in time. Follow-up on references at the end of the articles for more sources to examine
  • Refer books on a single topic by a single author or group of authors or books that contain chapters written by different authors
  • Next look for recent conference papers. Often, conference papers report the latest research developments. Contact authors of pertinent studies. Write or phone them, asking if they know of studies related to your area of interest
  • The easy access and ability to capture entire articles from the web make it attractive. However, check these articles carefully for authenticity and quality and be cautious about whether they represent systematic research.

The whole process of literature search[ 20 ] is summarised in Figure 1 .

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Process of literature search

Literature search provides not only an opportunity to learn more about a given topic but provides insight on how the topic was studied by previous analysts. It helps to interpret ideas, detect shortcomings and recognise opportunities. In short, systematic and well-organised research may help in designing a novel research.

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Conflicts of interest.

There are no conflicts of interest.

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A literature review surveys prior research published in books, scholarly articles, and any other sources relevant to a particular issue, area of research, or theory, and by so doing, provides a description, summary, and critical evaluation of these works in relation to the research problem being investigated. Literature reviews are designed to provide an overview of sources you have used in researching a particular topic and to demonstrate to your readers how your research fits within existing scholarship about the topic.

Fink, Arlene. Conducting Research Literature Reviews: From the Internet to Paper . Fourth edition. Thousand Oaks, CA: SAGE, 2014.

Importance of a Good Literature Review

A literature review may consist of simply a summary of key sources, but in the social sciences, a literature review usually has an organizational pattern and combines both summary and synthesis, often within specific conceptual categories . A summary is a recap of the important information of the source, but a synthesis is a re-organization, or a reshuffling, of that information in a way that informs how you are planning to investigate a research problem. The analytical features of a literature review might:

  • Give a new interpretation of old material or combine new with old interpretations,
  • Trace the intellectual progression of the field, including major debates,
  • Depending on the situation, evaluate the sources and advise the reader on the most pertinent or relevant research, or
  • Usually in the conclusion of a literature review, identify where gaps exist in how a problem has been researched to date.

Given this, the purpose of a literature review is to:

  • Place each work in the context of its contribution to understanding the research problem being studied.
  • Describe the relationship of each work to the others under consideration.
  • Identify new ways to interpret prior research.
  • Reveal any gaps that exist in the literature.
  • Resolve conflicts amongst seemingly contradictory previous studies.
  • Identify areas of prior scholarship to prevent duplication of effort.
  • Point the way in fulfilling a need for additional research.
  • Locate your own research within the context of existing literature [very important].

Fink, Arlene. Conducting Research Literature Reviews: From the Internet to Paper. 2nd ed. Thousand Oaks, CA: Sage, 2005; Hart, Chris. Doing a Literature Review: Releasing the Social Science Research Imagination . Thousand Oaks, CA: Sage Publications, 1998; Jesson, Jill. Doing Your Literature Review: Traditional and Systematic Techniques . Los Angeles, CA: SAGE, 2011; Knopf, Jeffrey W. "Doing a Literature Review." PS: Political Science and Politics 39 (January 2006): 127-132; Ridley, Diana. The Literature Review: A Step-by-Step Guide for Students . 2nd ed. Los Angeles, CA: SAGE, 2012.

Types of Literature Reviews

It is important to think of knowledge in a given field as consisting of three layers. First, there are the primary studies that researchers conduct and publish. Second are the reviews of those studies that summarize and offer new interpretations built from and often extending beyond the primary studies. Third, there are the perceptions, conclusions, opinion, and interpretations that are shared informally among scholars that become part of the body of epistemological traditions within the field.

In composing a literature review, it is important to note that it is often this third layer of knowledge that is cited as "true" even though it often has only a loose relationship to the primary studies and secondary literature reviews. Given this, while literature reviews are designed to provide an overview and synthesis of pertinent sources you have explored, there are a number of approaches you could adopt depending upon the type of analysis underpinning your study.

Argumentative Review This form examines literature selectively in order to support or refute an argument, deeply embedded assumption, or philosophical problem already established in the literature. The purpose is to develop a body of literature that establishes a contrarian viewpoint. Given the value-laden nature of some social science research [e.g., educational reform; immigration control], argumentative approaches to analyzing the literature can be a legitimate and important form of discourse. However, note that they can also introduce problems of bias when they are used to make summary claims of the sort found in systematic reviews [see below].

Integrative Review Considered a form of research that reviews, critiques, and synthesizes representative literature on a topic in an integrated way such that new frameworks and perspectives on the topic are generated. The body of literature includes all studies that address related or identical hypotheses or research problems. A well-done integrative review meets the same standards as primary research in regard to clarity, rigor, and replication. This is the most common form of review in the social sciences.

Historical Review Few things rest in isolation from historical precedent. Historical literature reviews focus on examining research throughout a period of time, often starting with the first time an issue, concept, theory, phenomena emerged in the literature, then tracing its evolution within the scholarship of a discipline. The purpose is to place research in a historical context to show familiarity with state-of-the-art developments and to identify the likely directions for future research.

Methodological Review A review does not always focus on what someone said [findings], but how they came about saying what they say [method of analysis]. Reviewing methods of analysis provides a framework of understanding at different levels [i.e. those of theory, substantive fields, research approaches, and data collection and analysis techniques], how researchers draw upon a wide variety of knowledge ranging from the conceptual level to practical documents for use in fieldwork in the areas of ontological and epistemological consideration, quantitative and qualitative integration, sampling, interviewing, data collection, and data analysis. This approach helps highlight ethical issues which you should be aware of and consider as you go through your own study.

Systematic Review This form consists of an overview of existing evidence pertinent to a clearly formulated research question, which uses pre-specified and standardized methods to identify and critically appraise relevant research, and to collect, report, and analyze data from the studies that are included in the review. The goal is to deliberately document, critically evaluate, and summarize scientifically all of the research about a clearly defined research problem . Typically it focuses on a very specific empirical question, often posed in a cause-and-effect form, such as "To what extent does A contribute to B?" This type of literature review is primarily applied to examining prior research studies in clinical medicine and allied health fields, but it is increasingly being used in the social sciences.

Theoretical Review The purpose of this form is to examine the corpus of theory that has accumulated in regard to an issue, concept, theory, phenomena. The theoretical literature review helps to establish what theories already exist, the relationships between them, to what degree the existing theories have been investigated, and to develop new hypotheses to be tested. Often this form is used to help establish a lack of appropriate theories or reveal that current theories are inadequate for explaining new or emerging research problems. The unit of analysis can focus on a theoretical concept or a whole theory or framework.

NOTE : Most often the literature review will incorporate some combination of types. For example, a review that examines literature supporting or refuting an argument, assumption, or philosophical problem related to the research problem will also need to include writing supported by sources that establish the history of these arguments in the literature.

Baumeister, Roy F. and Mark R. Leary. "Writing Narrative Literature Reviews."  Review of General Psychology 1 (September 1997): 311-320; Mark R. Fink, Arlene. Conducting Research Literature Reviews: From the Internet to Paper . 2nd ed. Thousand Oaks, CA: Sage, 2005; Hart, Chris. Doing a Literature Review: Releasing the Social Science Research Imagination . Thousand Oaks, CA: Sage Publications, 1998; Kennedy, Mary M. "Defining a Literature." Educational Researcher 36 (April 2007): 139-147; Petticrew, Mark and Helen Roberts. Systematic Reviews in the Social Sciences: A Practical Guide . Malden, MA: Blackwell Publishers, 2006; Torracro, Richard. "Writing Integrative Literature Reviews: Guidelines and Examples." Human Resource Development Review 4 (September 2005): 356-367; Rocco, Tonette S. and Maria S. Plakhotnik. "Literature Reviews, Conceptual Frameworks, and Theoretical Frameworks: Terms, Functions, and Distinctions." Human Ressource Development Review 8 (March 2008): 120-130; Sutton, Anthea. Systematic Approaches to a Successful Literature Review . Los Angeles, CA: Sage Publications, 2016.

Structure and Writing Style

I.  Thinking About Your Literature Review

The structure of a literature review should include the following in support of understanding the research problem :

  • An overview of the subject, issue, or theory under consideration, along with the objectives of the literature review,
  • Division of works under review into themes or categories [e.g. works that support a particular position, those against, and those offering alternative approaches entirely],
  • An explanation of how each work is similar to and how it varies from the others,
  • Conclusions as to which pieces are best considered in their argument, are most convincing of their opinions, and make the greatest contribution to the understanding and development of their area of research.

The critical evaluation of each work should consider :

  • Provenance -- what are the author's credentials? Are the author's arguments supported by evidence [e.g. primary historical material, case studies, narratives, statistics, recent scientific findings]?
  • Methodology -- were the techniques used to identify, gather, and analyze the data appropriate to addressing the research problem? Was the sample size appropriate? Were the results effectively interpreted and reported?
  • Objectivity -- is the author's perspective even-handed or prejudicial? Is contrary data considered or is certain pertinent information ignored to prove the author's point?
  • Persuasiveness -- which of the author's theses are most convincing or least convincing?
  • Validity -- are the author's arguments and conclusions convincing? Does the work ultimately contribute in any significant way to an understanding of the subject?

II.  Development of the Literature Review

Four Basic Stages of Writing 1.  Problem formulation -- which topic or field is being examined and what are its component issues? 2.  Literature search -- finding materials relevant to the subject being explored. 3.  Data evaluation -- determining which literature makes a significant contribution to the understanding of the topic. 4.  Analysis and interpretation -- discussing the findings and conclusions of pertinent literature.

Consider the following issues before writing the literature review: Clarify If your assignment is not specific about what form your literature review should take, seek clarification from your professor by asking these questions: 1.  Roughly how many sources would be appropriate to include? 2.  What types of sources should I review (books, journal articles, websites; scholarly versus popular sources)? 3.  Should I summarize, synthesize, or critique sources by discussing a common theme or issue? 4.  Should I evaluate the sources in any way beyond evaluating how they relate to understanding the research problem? 5.  Should I provide subheadings and other background information, such as definitions and/or a history? Find Models Use the exercise of reviewing the literature to examine how authors in your discipline or area of interest have composed their literature review sections. Read them to get a sense of the types of themes you might want to look for in your own research or to identify ways to organize your final review. The bibliography or reference section of sources you've already read, such as required readings in the course syllabus, are also excellent entry points into your own research. Narrow the Topic The narrower your topic, the easier it will be to limit the number of sources you need to read in order to obtain a good survey of relevant resources. Your professor will probably not expect you to read everything that's available about the topic, but you'll make the act of reviewing easier if you first limit scope of the research problem. A good strategy is to begin by searching the USC Libraries Catalog for recent books about the topic and review the table of contents for chapters that focuses on specific issues. You can also review the indexes of books to find references to specific issues that can serve as the focus of your research. For example, a book surveying the history of the Israeli-Palestinian conflict may include a chapter on the role Egypt has played in mediating the conflict, or look in the index for the pages where Egypt is mentioned in the text. Consider Whether Your Sources are Current Some disciplines require that you use information that is as current as possible. This is particularly true in disciplines in medicine and the sciences where research conducted becomes obsolete very quickly as new discoveries are made. However, when writing a review in the social sciences, a survey of the history of the literature may be required. In other words, a complete understanding the research problem requires you to deliberately examine how knowledge and perspectives have changed over time. Sort through other current bibliographies or literature reviews in the field to get a sense of what your discipline expects. You can also use this method to explore what is considered by scholars to be a "hot topic" and what is not.

III.  Ways to Organize Your Literature Review

Chronology of Events If your review follows the chronological method, you could write about the materials according to when they were published. This approach should only be followed if a clear path of research building on previous research can be identified and that these trends follow a clear chronological order of development. For example, a literature review that focuses on continuing research about the emergence of German economic power after the fall of the Soviet Union. By Publication Order your sources by publication chronology, then, only if the order demonstrates a more important trend. For instance, you could order a review of literature on environmental studies of brown fields if the progression revealed, for example, a change in the soil collection practices of the researchers who wrote and/or conducted the studies. Thematic [“conceptual categories”] A thematic literature review is the most common approach to summarizing prior research in the social and behavioral sciences. Thematic reviews are organized around a topic or issue, rather than the progression of time, although the progression of time may still be incorporated into a thematic review. For example, a review of the Internet’s impact on American presidential politics could focus on the development of online political satire. While the study focuses on one topic, the Internet’s impact on American presidential politics, it would still be organized chronologically reflecting technological developments in media. The difference in this example between a "chronological" and a "thematic" approach is what is emphasized the most: themes related to the role of the Internet in presidential politics. Note that more authentic thematic reviews tend to break away from chronological order. A review organized in this manner would shift between time periods within each section according to the point being made. Methodological A methodological approach focuses on the methods utilized by the researcher. For the Internet in American presidential politics project, one methodological approach would be to look at cultural differences between the portrayal of American presidents on American, British, and French websites. Or the review might focus on the fundraising impact of the Internet on a particular political party. A methodological scope will influence either the types of documents in the review or the way in which these documents are discussed.

Other Sections of Your Literature Review Once you've decided on the organizational method for your literature review, the sections you need to include in the paper should be easy to figure out because they arise from your organizational strategy. In other words, a chronological review would have subsections for each vital time period; a thematic review would have subtopics based upon factors that relate to the theme or issue. However, sometimes you may need to add additional sections that are necessary for your study, but do not fit in the organizational strategy of the body. What other sections you include in the body is up to you. However, only include what is necessary for the reader to locate your study within the larger scholarship about the research problem.

Here are examples of other sections, usually in the form of a single paragraph, you may need to include depending on the type of review you write:

  • Current Situation : Information necessary to understand the current topic or focus of the literature review.
  • Sources Used : Describes the methods and resources [e.g., databases] you used to identify the literature you reviewed.
  • History : The chronological progression of the field, the research literature, or an idea that is necessary to understand the literature review, if the body of the literature review is not already a chronology.
  • Selection Methods : Criteria you used to select (and perhaps exclude) sources in your literature review. For instance, you might explain that your review includes only peer-reviewed [i.e., scholarly] sources.
  • Standards : Description of the way in which you present your information.
  • Questions for Further Research : What questions about the field has the review sparked? How will you further your research as a result of the review?

IV.  Writing Your Literature Review

Once you've settled on how to organize your literature review, you're ready to write each section. When writing your review, keep in mind these issues.

Use Evidence A literature review section is, in this sense, just like any other academic research paper. Your interpretation of the available sources must be backed up with evidence [citations] that demonstrates that what you are saying is valid. Be Selective Select only the most important points in each source to highlight in the review. The type of information you choose to mention should relate directly to the research problem, whether it is thematic, methodological, or chronological. Related items that provide additional information, but that are not key to understanding the research problem, can be included in a list of further readings . Use Quotes Sparingly Some short quotes are appropriate if you want to emphasize a point, or if what an author stated cannot be easily paraphrased. Sometimes you may need to quote certain terminology that was coined by the author, is not common knowledge, or taken directly from the study. Do not use extensive quotes as a substitute for using your own words in reviewing the literature. Summarize and Synthesize Remember to summarize and synthesize your sources within each thematic paragraph as well as throughout the review. Recapitulate important features of a research study, but then synthesize it by rephrasing the study's significance and relating it to your own work and the work of others. Keep Your Own Voice While the literature review presents others' ideas, your voice [the writer's] should remain front and center. For example, weave references to other sources into what you are writing but maintain your own voice by starting and ending the paragraph with your own ideas and wording. Use Caution When Paraphrasing When paraphrasing a source that is not your own, be sure to represent the author's information or opinions accurately and in your own words. Even when paraphrasing an author’s work, you still must provide a citation to that work.

V.  Common Mistakes to Avoid

These are the most common mistakes made in reviewing social science research literature.

  • Sources in your literature review do not clearly relate to the research problem;
  • You do not take sufficient time to define and identify the most relevant sources to use in the literature review related to the research problem;
  • Relies exclusively on secondary analytical sources rather than including relevant primary research studies or data;
  • Uncritically accepts another researcher's findings and interpretations as valid, rather than examining critically all aspects of the research design and analysis;
  • Does not describe the search procedures that were used in identifying the literature to review;
  • Reports isolated statistical results rather than synthesizing them in chi-squared or meta-analytic methods; and,
  • Only includes research that validates assumptions and does not consider contrary findings and alternative interpretations found in the literature.

Cook, Kathleen E. and Elise Murowchick. “Do Literature Review Skills Transfer from One Course to Another?” Psychology Learning and Teaching 13 (March 2014): 3-11; Fink, Arlene. Conducting Research Literature Reviews: From the Internet to Paper . 2nd ed. Thousand Oaks, CA: Sage, 2005; Hart, Chris. Doing a Literature Review: Releasing the Social Science Research Imagination . Thousand Oaks, CA: Sage Publications, 1998; Jesson, Jill. Doing Your Literature Review: Traditional and Systematic Techniques . London: SAGE, 2011; Literature Review Handout. Online Writing Center. Liberty University; Literature Reviews. The Writing Center. University of North Carolina; Onwuegbuzie, Anthony J. and Rebecca Frels. Seven Steps to a Comprehensive Literature Review: A Multimodal and Cultural Approach . Los Angeles, CA: SAGE, 2016; Ridley, Diana. The Literature Review: A Step-by-Step Guide for Students . 2nd ed. Los Angeles, CA: SAGE, 2012; Randolph, Justus J. “A Guide to Writing the Dissertation Literature Review." Practical Assessment, Research, and Evaluation. vol. 14, June 2009; Sutton, Anthea. Systematic Approaches to a Successful Literature Review . Los Angeles, CA: Sage Publications, 2016; Taylor, Dena. The Literature Review: A Few Tips On Conducting It. University College Writing Centre. University of Toronto; Writing a Literature Review. Academic Skills Centre. University of Canberra.

Writing Tip

Break Out of Your Disciplinary Box!

Thinking interdisciplinarily about a research problem can be a rewarding exercise in applying new ideas, theories, or concepts to an old problem. For example, what might cultural anthropologists say about the continuing conflict in the Middle East? In what ways might geographers view the need for better distribution of social service agencies in large cities than how social workers might study the issue? You don’t want to substitute a thorough review of core research literature in your discipline for studies conducted in other fields of study. However, particularly in the social sciences, thinking about research problems from multiple vectors is a key strategy for finding new solutions to a problem or gaining a new perspective. Consult with a librarian about identifying research databases in other disciplines; almost every field of study has at least one comprehensive database devoted to indexing its research literature.

Frodeman, Robert. The Oxford Handbook of Interdisciplinarity . New York: Oxford University Press, 2010.

Another Writing Tip

Don't Just Review for Content!

While conducting a review of the literature, maximize the time you devote to writing this part of your paper by thinking broadly about what you should be looking for and evaluating. Review not just what scholars are saying, but how are they saying it. Some questions to ask:

  • How are they organizing their ideas?
  • What methods have they used to study the problem?
  • What theories have been used to explain, predict, or understand their research problem?
  • What sources have they cited to support their conclusions?
  • How have they used non-textual elements [e.g., charts, graphs, figures, etc.] to illustrate key points?

When you begin to write your literature review section, you'll be glad you dug deeper into how the research was designed and constructed because it establishes a means for developing more substantial analysis and interpretation of the research problem.

Hart, Chris. Doing a Literature Review: Releasing the Social Science Research Imagination . Thousand Oaks, CA: Sage Publications, 1 998.

Yet Another Writing Tip

When Do I Know I Can Stop Looking and Move On?

Here are several strategies you can utilize to assess whether you've thoroughly reviewed the literature:

  • Look for repeating patterns in the research findings . If the same thing is being said, just by different people, then this likely demonstrates that the research problem has hit a conceptual dead end. At this point consider: Does your study extend current research?  Does it forge a new path? Or, does is merely add more of the same thing being said?
  • Look at sources the authors cite to in their work . If you begin to see the same researchers cited again and again, then this is often an indication that no new ideas have been generated to address the research problem.
  • Search Google Scholar to identify who has subsequently cited leading scholars already identified in your literature review [see next sub-tab]. This is called citation tracking and there are a number of sources that can help you identify who has cited whom, particularly scholars from outside of your discipline. Here again, if the same authors are being cited again and again, this may indicate no new literature has been written on the topic.

Onwuegbuzie, Anthony J. and Rebecca Frels. Seven Steps to a Comprehensive Literature Review: A Multimodal and Cultural Approach . Los Angeles, CA: Sage, 2016; Sutton, Anthea. Systematic Approaches to a Successful Literature Review . Los Angeles, CA: Sage Publications, 2016.

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  • Methodology
  • Open access
  • Published: 11 October 2016

Reviewing the research methods literature: principles and strategies illustrated by a systematic overview of sampling in qualitative research

  • Stephen J. Gentles 1 , 4 ,
  • Cathy Charles 1 ,
  • David B. Nicholas 2 ,
  • Jenny Ploeg 3 &
  • K. Ann McKibbon 1  

Systematic Reviews volume  5 , Article number:  172 ( 2016 ) Cite this article

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Overviews of methods are potentially useful means to increase clarity and enhance collective understanding of specific methods topics that may be characterized by ambiguity, inconsistency, or a lack of comprehensiveness. This type of review represents a distinct literature synthesis method, although to date, its methodology remains relatively undeveloped despite several aspects that demand unique review procedures. The purpose of this paper is to initiate discussion about what a rigorous systematic approach to reviews of methods, referred to here as systematic methods overviews , might look like by providing tentative suggestions for approaching specific challenges likely to be encountered. The guidance offered here was derived from experience conducting a systematic methods overview on the topic of sampling in qualitative research.

The guidance is organized into several principles that highlight specific objectives for this type of review given the common challenges that must be overcome to achieve them. Optional strategies for achieving each principle are also proposed, along with discussion of how they were successfully implemented in the overview on sampling. We describe seven paired principles and strategies that address the following aspects: delimiting the initial set of publications to consider, searching beyond standard bibliographic databases, searching without the availability of relevant metadata, selecting publications on purposeful conceptual grounds, defining concepts and other information to abstract iteratively, accounting for inconsistent terminology used to describe specific methods topics, and generating rigorous verifiable analytic interpretations. Since a broad aim in systematic methods overviews is to describe and interpret the relevant literature in qualitative terms, we suggest that iterative decision making at various stages of the review process, and a rigorous qualitative approach to analysis are necessary features of this review type.

Conclusions

We believe that the principles and strategies provided here will be useful to anyone choosing to undertake a systematic methods overview. This paper represents an initial effort to promote high quality critical evaluations of the literature regarding problematic methods topics, which have the potential to promote clearer, shared understandings, and accelerate advances in research methods. Further work is warranted to develop more definitive guidance.

Peer Review reports

While reviews of methods are not new, they represent a distinct review type whose methodology remains relatively under-addressed in the literature despite the clear implications for unique review procedures. One of few examples to describe it is a chapter containing reflections of two contributing authors in a book of 21 reviews on methodological topics compiled for the British National Health Service, Health Technology Assessment Program [ 1 ]. Notable is their observation of how the differences between the methods reviews and conventional quantitative systematic reviews, specifically attributable to their varying content and purpose, have implications for defining what qualifies as systematic. While the authors describe general aspects of “systematicity” (including rigorous application of a methodical search, abstraction, and analysis), they also describe a high degree of variation within the category of methods reviews itself and so offer little in the way of concrete guidance. In this paper, we present tentative concrete guidance, in the form of a preliminary set of proposed principles and optional strategies, for a rigorous systematic approach to reviewing and evaluating the literature on quantitative or qualitative methods topics. For purposes of this article, we have used the term systematic methods overview to emphasize the notion of a systematic approach to such reviews.

The conventional focus of rigorous literature reviews (i.e., review types for which systematic methods have been codified, including the various approaches to quantitative systematic reviews [ 2 – 4 ], and the numerous forms of qualitative and mixed methods literature synthesis [ 5 – 10 ]) is to synthesize empirical research findings from multiple studies. By contrast, the focus of overviews of methods, including the systematic approach we advocate, is to synthesize guidance on methods topics. The literature consulted for such reviews may include the methods literature, methods-relevant sections of empirical research reports, or both. Thus, this paper adds to previous work published in this journal—namely, recent preliminary guidance for conducting reviews of theory [ 11 ]—that has extended the application of systematic review methods to novel review types that are concerned with subject matter other than empirical research findings.

Published examples of methods overviews illustrate the varying objectives they can have. One objective is to establish methodological standards for appraisal purposes. For example, reviews of existing quality appraisal standards have been used to propose universal standards for appraising the quality of primary qualitative research [ 12 ] or evaluating qualitative research reports [ 13 ]. A second objective is to survey the methods-relevant sections of empirical research reports to establish current practices on methods use and reporting practices, which Moher and colleagues [ 14 ] recommend as a means for establishing the needs to be addressed in reporting guidelines (see, for example [ 15 , 16 ]). A third objective for a methods review is to offer clarity and enhance collective understanding regarding a specific methods topic that may be characterized by ambiguity, inconsistency, or a lack of comprehensiveness within the available methods literature. An example of this is a overview whose objective was to review the inconsistent definitions of intention-to-treat analysis (the methodologically preferred approach to analyze randomized controlled trial data) that have been offered in the methods literature and propose a solution for improving conceptual clarity [ 17 ]. Such reviews are warranted because students and researchers who must learn or apply research methods typically lack the time to systematically search, retrieve, review, and compare the available literature to develop a thorough and critical sense of the varied approaches regarding certain controversial or ambiguous methods topics.

While systematic methods overviews , as a review type, include both reviews of the methods literature and reviews of methods-relevant sections from empirical study reports, the guidance provided here is primarily applicable to reviews of the methods literature since it was derived from the experience of conducting such a review [ 18 ], described below. To our knowledge, there are no well-developed proposals on how to rigorously conduct such reviews. Such guidance would have the potential to improve the thoroughness and credibility of critical evaluations of the methods literature, which could increase their utility as a tool for generating understandings that advance research methods, both qualitative and quantitative. Our aim in this paper is thus to initiate discussion about what might constitute a rigorous approach to systematic methods overviews. While we hope to promote rigor in the conduct of systematic methods overviews wherever possible, we do not wish to suggest that all methods overviews need be conducted to the same standard. Rather, we believe that the level of rigor may need to be tailored pragmatically to the specific review objectives, which may not always justify the resource requirements of an intensive review process.

The example systematic methods overview on sampling in qualitative research

The principles and strategies we propose in this paper are derived from experience conducting a systematic methods overview on the topic of sampling in qualitative research [ 18 ]. The main objective of that methods overview was to bring clarity and deeper understanding of the prominent concepts related to sampling in qualitative research (purposeful sampling strategies, saturation, etc.). Specifically, we interpreted the available guidance, commenting on areas lacking clarity, consistency, or comprehensiveness (without proposing any recommendations on how to do sampling). This was achieved by a comparative and critical analysis of publications representing the most influential (i.e., highly cited) guidance across several methodological traditions in qualitative research.

The specific methods and procedures for the overview on sampling [ 18 ] from which our proposals are derived were developed both after soliciting initial input from local experts in qualitative research and an expert health librarian (KAM) and through ongoing careful deliberation throughout the review process. To summarize, in that review, we employed a transparent and rigorous approach to search the methods literature, selected publications for inclusion according to a purposeful and iterative process, abstracted textual data using structured abstraction forms, and analyzed (synthesized) the data using a systematic multi-step approach featuring abstraction of text, summary of information in matrices, and analytic comparisons.

For this article, we reflected on both the problems and challenges encountered at different stages of the review and our means for selecting justifiable procedures to deal with them. Several principles were then derived by considering the generic nature of these problems, while the generalizable aspects of the procedures used to address them formed the basis of optional strategies. Further details of the specific methods and procedures used in the overview on qualitative sampling are provided below to illustrate both the types of objectives and challenges that reviewers will likely need to consider and our approach to implementing each of the principles and strategies.

Organization of the guidance into principles and strategies

For the purposes of this article, principles are general statements outlining what we propose are important aims or considerations within a particular review process, given the unique objectives or challenges to be overcome with this type of review. These statements follow the general format, “considering the objective or challenge of X, we propose Y to be an important aim or consideration.” Strategies are optional and flexible approaches for implementing the previous principle outlined. Thus, generic challenges give rise to principles, which in turn give rise to strategies.

We organize the principles and strategies below into three sections corresponding to processes characteristic of most systematic literature synthesis approaches: literature identification and selection ; data abstraction from the publications selected for inclusion; and analysis , including critical appraisal and synthesis of the abstracted data. Within each section, we also describe the specific methodological decisions and procedures used in the overview on sampling in qualitative research [ 18 ] to illustrate how the principles and strategies for each review process were applied and implemented in a specific case. We expect this guidance and accompanying illustrations will be useful for anyone considering engaging in a methods overview, particularly those who may be familiar with conventional systematic review methods but may not yet appreciate some of the challenges specific to reviewing the methods literature.

Results and discussion

Literature identification and selection.

The identification and selection process includes search and retrieval of publications and the development and application of inclusion and exclusion criteria to select the publications that will be abstracted and analyzed in the final review. Literature identification and selection for overviews of the methods literature is challenging and potentially more resource-intensive than for most reviews of empirical research. This is true for several reasons that we describe below, alongside discussion of the potential solutions. Additionally, we suggest in this section how the selection procedures can be chosen to match the specific analytic approach used in methods overviews.

Delimiting a manageable set of publications

One aspect of methods overviews that can make identification and selection challenging is the fact that the universe of literature containing potentially relevant information regarding most methods-related topics is expansive and often unmanageably so. Reviewers are faced with two large categories of literature: the methods literature , where the possible publication types include journal articles, books, and book chapters; and the methods-relevant sections of empirical study reports , where the possible publication types include journal articles, monographs, books, theses, and conference proceedings. In our systematic overview of sampling in qualitative research, exhaustively searching (including retrieval and first-pass screening) all publication types across both categories of literature for information on a single methods-related topic was too burdensome to be feasible. The following proposed principle follows from the need to delimit a manageable set of literature for the review.

Principle #1:

Considering the broad universe of potentially relevant literature, we propose that an important objective early in the identification and selection stage is to delimit a manageable set of methods-relevant publications in accordance with the objectives of the methods overview.

Strategy #1:

To limit the set of methods-relevant publications that must be managed in the selection process, reviewers have the option to initially review only the methods literature, and exclude the methods-relevant sections of empirical study reports, provided this aligns with the review’s particular objectives.

We propose that reviewers are justified in choosing to select only the methods literature when the objective is to map out the range of recognized concepts relevant to a methods topic, to summarize the most authoritative or influential definitions or meanings for methods-related concepts, or to demonstrate a problematic lack of clarity regarding a widely established methods-related concept and potentially make recommendations for a preferred approach to the methods topic in question. For example, in the case of the methods overview on sampling [ 18 ], the primary aim was to define areas lacking in clarity for multiple widely established sampling-related topics. In the review on intention-to-treat in the context of missing outcome data [ 17 ], the authors identified a lack of clarity based on multiple inconsistent definitions in the literature and went on to recommend separating the issue of how to handle missing outcome data from the issue of whether an intention-to-treat analysis can be claimed.

In contrast to strategy #1, it may be appropriate to select the methods-relevant sections of empirical study reports when the objective is to illustrate how a methods concept is operationalized in research practice or reported by authors. For example, one could review all the publications in 2 years’ worth of issues of five high-impact field-related journals to answer questions about how researchers describe implementing a particular method or approach, or to quantify how consistently they define or report using it. Such reviews are often used to highlight gaps in the reporting practices regarding specific methods, which may be used to justify items to address in reporting guidelines (for example, [ 14 – 16 ]).

It is worth recognizing that other authors have advocated broader positions regarding the scope of literature to be considered in a review, expanding on our perspective. Suri [ 10 ] (who, like us, emphasizes how different sampling strategies are suitable for different literature synthesis objectives) has, for example, described a two-stage literature sampling procedure (pp. 96–97). First, reviewers use an initial approach to conduct a broad overview of the field—for reviews of methods topics, this would entail an initial review of the research methods literature. This is followed by a second more focused stage in which practical examples are purposefully selected—for methods reviews, this would involve sampling the empirical literature to illustrate key themes and variations. While this approach is seductive in its capacity to generate more in depth and interpretive analytic findings, some reviewers may consider it too resource-intensive to include the second step no matter how selective the purposeful sampling. In the overview on sampling where we stopped after the first stage [ 18 ], we discussed our selective focus on the methods literature as a limitation that left opportunities for further analysis of the literature. We explicitly recommended, for example, that theoretical sampling was a topic for which a future review of the methods sections of empirical reports was justified to answer specific questions identified in the primary review.

Ultimately, reviewers must make pragmatic decisions that balance resource considerations, combined with informed predictions about the depth and complexity of literature available on their topic, with the stated objectives of their review. The remaining principles and strategies apply primarily to overviews that include the methods literature, although some aspects may be relevant to reviews that include empirical study reports.

Searching beyond standard bibliographic databases

An important reality affecting identification and selection in overviews of the methods literature is the increased likelihood for relevant publications to be located in sources other than journal articles (which is usually not the case for overviews of empirical research, where journal articles generally represent the primary publication type). In the overview on sampling [ 18 ], out of 41 full-text publications retrieved and reviewed, only 4 were journal articles, while 37 were books or book chapters. Since many books and book chapters did not exist electronically, their full text had to be physically retrieved in hardcopy, while 11 publications were retrievable only through interlibrary loan or purchase request. The tasks associated with such retrieval are substantially more time-consuming than electronic retrieval. Since a substantial proportion of methods-related guidance may be located in publication types that are less comprehensively indexed in standard bibliographic databases, identification and retrieval thus become complicated processes.

Principle #2:

Considering that important sources of methods guidance can be located in non-journal publication types (e.g., books, book chapters) that tend to be poorly indexed in standard bibliographic databases, it is important to consider alternative search methods for identifying relevant publications to be further screened for inclusion.

Strategy #2:

To identify books, book chapters, and other non-journal publication types not thoroughly indexed in standard bibliographic databases, reviewers may choose to consult one or more of the following less standard sources: Google Scholar, publisher web sites, or expert opinion.

In the case of the overview on sampling in qualitative research [ 18 ], Google Scholar had two advantages over other standard bibliographic databases: it indexes and returns records of books and book chapters likely to contain guidance on qualitative research methods topics; and it has been validated as providing higher citation counts than ISI Web of Science (a producer of numerous bibliographic databases accessible through institutional subscription) for several non-biomedical disciplines including the social sciences where qualitative research methods are prominently used [ 19 – 21 ]. While we identified numerous useful publications by consulting experts, the author publication lists generated through Google Scholar searches were uniquely useful to identify more recent editions of methods books identified by experts.

Searching without relevant metadata

Determining what publications to select for inclusion in the overview on sampling [ 18 ] could only rarely be accomplished by reviewing the publication’s metadata. This was because for the many books and other non-journal type publications we identified as possibly relevant, the potential content of interest would be located in only a subsection of the publication. In this common scenario for reviews of the methods literature (as opposed to methods overviews that include empirical study reports), reviewers will often be unable to employ standard title, abstract, and keyword database searching or screening as a means for selecting publications.

Principle #3:

Considering that the presence of information about the topic of interest may not be indicated in the metadata for books and similar publication types, it is important to consider other means of identifying potentially useful publications for further screening.

Strategy #3:

One approach to identifying potentially useful books and similar publication types is to consider what classes of such publications (e.g., all methods manuals for a certain research approach) are likely to contain relevant content, then identify, retrieve, and review the full text of corresponding publications to determine whether they contain information on the topic of interest.

In the example of the overview on sampling in qualitative research [ 18 ], the topic of interest (sampling) was one of numerous topics covered in the general qualitative research methods manuals. Consequently, examples from this class of publications first had to be identified for retrieval according to non-keyword-dependent criteria. Thus, all methods manuals within the three research traditions reviewed (grounded theory, phenomenology, and case study) that might contain discussion of sampling were sought through Google Scholar and expert opinion, their full text obtained, and hand-searched for relevant content to determine eligibility. We used tables of contents and index sections of books to aid this hand searching.

Purposefully selecting literature on conceptual grounds

A final consideration in methods overviews relates to the type of analysis used to generate the review findings. Unlike quantitative systematic reviews where reviewers aim for accurate or unbiased quantitative estimates—something that requires identifying and selecting the literature exhaustively to obtain all relevant data available (i.e., a complete sample)—in methods overviews, reviewers must describe and interpret the relevant literature in qualitative terms to achieve review objectives. In other words, the aim in methods overviews is to seek coverage of the qualitative concepts relevant to the methods topic at hand. For example, in the overview of sampling in qualitative research [ 18 ], achieving review objectives entailed providing conceptual coverage of eight sampling-related topics that emerged as key domains. The following principle recognizes that literature sampling should therefore support generating qualitative conceptual data as the input to analysis.

Principle #4:

Since the analytic findings of a systematic methods overview are generated through qualitative description and interpretation of the literature on a specified topic, selection of the literature should be guided by a purposeful strategy designed to achieve adequate conceptual coverage (i.e., representing an appropriate degree of variation in relevant ideas) of the topic according to objectives of the review.

Strategy #4:

One strategy for choosing the purposeful approach to use in selecting the literature according to the review objectives is to consider whether those objectives imply exploring concepts either at a broad overview level, in which case combining maximum variation selection with a strategy that limits yield (e.g., critical case, politically important, or sampling for influence—described below) may be appropriate; or in depth, in which case purposeful approaches aimed at revealing innovative cases will likely be necessary.

In the methods overview on sampling, the implied scope was broad since we set out to review publications on sampling across three divergent qualitative research traditions—grounded theory, phenomenology, and case study—to facilitate making informative conceptual comparisons. Such an approach would be analogous to maximum variation sampling.

At the same time, the purpose of that review was to critically interrogate the clarity, consistency, and comprehensiveness of literature from these traditions that was “most likely to have widely influenced students’ and researchers’ ideas about sampling” (p. 1774) [ 18 ]. In other words, we explicitly set out to review and critique the most established and influential (and therefore dominant) literature, since this represents a common basis of knowledge among students and researchers seeking understanding or practical guidance on sampling in qualitative research. To achieve this objective, we purposefully sampled publications according to the criterion of influence , which we operationalized as how often an author or publication has been referenced in print or informal discourse. This second sampling approach also limited the literature we needed to consider within our broad scope review to a manageable amount.

To operationalize this strategy of sampling for influence , we sought to identify both the most influential authors within a qualitative research tradition (all of whose citations were subsequently screened) and the most influential publications on the topic of interest by non-influential authors. This involved a flexible approach that combined multiple indicators of influence to avoid the dilemma that any single indicator might provide inadequate coverage. These indicators included bibliometric data (h-index for author influence [ 22 ]; number of cites for publication influence), expert opinion, and cross-references in the literature (i.e., snowball sampling). As a final selection criterion, a publication was included only if it made an original contribution in terms of novel guidance regarding sampling or a related concept; thus, purely secondary sources were excluded. Publish or Perish software (Anne-Wil Harzing; available at http://www.harzing.com/resources/publish-or-perish ) was used to generate bibliometric data via the Google Scholar database. Figure  1 illustrates how identification and selection in the methods overview on sampling was a multi-faceted and iterative process. The authors selected as influential, and the publications selected for inclusion or exclusion are listed in Additional file 1 (Matrices 1, 2a, 2b).

Literature identification and selection process used in the methods overview on sampling [ 18 ]

In summary, the strategies of seeking maximum variation and sampling for influence were employed in the sampling overview to meet the specific review objectives described. Reviewers will need to consider the full range of purposeful literature sampling approaches at their disposal in deciding what best matches the specific aims of their own reviews. Suri [ 10 ] has recently retooled Patton’s well-known typology of purposeful sampling strategies (originally intended for primary research) for application to literature synthesis, providing a useful resource in this respect.

Data abstraction

The purpose of data abstraction in rigorous literature reviews is to locate and record all data relevant to the topic of interest from the full text of included publications, making them available for subsequent analysis. Conventionally, a data abstraction form—consisting of numerous distinct conceptually defined fields to which corresponding information from the source publication is recorded—is developed and employed. There are several challenges, however, to the processes of developing the abstraction form and abstracting the data itself when conducting methods overviews, which we address here. Some of these problems and their solutions may be familiar to those who have conducted qualitative literature syntheses, which are similarly conceptual.

Iteratively defining conceptual information to abstract

In the overview on sampling [ 18 ], while we surveyed multiple sources beforehand to develop a list of concepts relevant for abstraction (e.g., purposeful sampling strategies, saturation, sample size), there was no way for us to anticipate some concepts prior to encountering them in the review process. Indeed, in many cases, reviewers are unable to determine the complete set of methods-related concepts that will be the focus of the final review a priori without having systematically reviewed the publications to be included. Thus, defining what information to abstract beforehand may not be feasible.

Principle #5:

Considering the potential impracticality of defining a complete set of relevant methods-related concepts from a body of literature one has not yet systematically read, selecting and defining fields for data abstraction must often be undertaken iteratively. Thus, concepts to be abstracted can be expected to grow and change as data abstraction proceeds.

Strategy #5:

Reviewers can develop an initial form or set of concepts for abstraction purposes according to standard methods (e.g., incorporating expert feedback, pilot testing) and remain attentive to the need to iteratively revise it as concepts are added or modified during the review. Reviewers should document revisions and return to re-abstract data from previously abstracted publications as the new data requirements are determined.

In the sampling overview [ 18 ], we developed and maintained the abstraction form in Microsoft Word. We derived the initial set of abstraction fields from our own knowledge of relevant sampling-related concepts, consultation with local experts, and reviewing a pilot sample of publications. Since the publications in this review included a large proportion of books, the abstraction process often began by flagging the broad sections within a publication containing topic-relevant information for detailed review to identify text to abstract. When reviewing flagged text, the reviewer occasionally encountered an unanticipated concept significant enough to warrant being added as a new field to the abstraction form. For example, a field was added to capture how authors described the timing of sampling decisions, whether before (a priori) or after (ongoing) starting data collection, or whether this was unclear. In these cases, we systematically documented the modification to the form and returned to previously abstracted publications to abstract any information that might be relevant to the new field.

The logic of this strategy is analogous to the logic used in a form of research synthesis called best fit framework synthesis (BFFS) [ 23 – 25 ]. In that method, reviewers initially code evidence using an a priori framework they have selected. When evidence cannot be accommodated by the selected framework, reviewers then develop new themes or concepts from which they construct a new expanded framework. Both the strategy proposed and the BFFS approach to research synthesis are notable for their rigorous and transparent means to adapt a final set of concepts to the content under review.

Accounting for inconsistent terminology

An important complication affecting the abstraction process in methods overviews is that the language used by authors to describe methods-related concepts can easily vary across publications. For example, authors from different qualitative research traditions often use different terms for similar methods-related concepts. Furthermore, as we found in the sampling overview [ 18 ], there may be cases where no identifiable term, phrase, or label for a methods-related concept is used at all, and a description of it is given instead. This can make searching the text for relevant concepts based on keywords unreliable.

Principle #6:

Since accepted terms may not be used consistently to refer to methods concepts, it is necessary to rely on the definitions for concepts, rather than keywords, to identify relevant information in the publication to abstract.

Strategy #6:

An effective means to systematically identify relevant information is to develop and iteratively adjust written definitions for key concepts (corresponding to abstraction fields) that are consistent with and as inclusive of as much of the literature reviewed as possible. Reviewers then seek information that matches these definitions (rather than keywords) when scanning a publication for relevant data to abstract.

In the abstraction process for the sampling overview [ 18 ], we noted the several concepts of interest to the review for which abstraction by keyword was particularly problematic due to inconsistent terminology across publications: sampling , purposeful sampling , sampling strategy , and saturation (for examples, see Additional file 1 , Matrices 3a, 3b, 4). We iteratively developed definitions for these concepts by abstracting text from publications that either provided an explicit definition or from which an implicit definition could be derived, which was recorded in fields dedicated to the concept’s definition. Using a method of constant comparison, we used text from definition fields to inform and modify a centrally maintained definition of the corresponding concept to optimize its fit and inclusiveness with the literature reviewed. Table  1 shows, as an example, the final definition constructed in this way for one of the central concepts of the review, qualitative sampling .

We applied iteratively developed definitions when making decisions about what specific text to abstract for an existing field, which allowed us to abstract concept-relevant data even if no recognized keyword was used. For example, this was the case for the sampling-related concept, saturation , where the relevant text available for abstraction in one publication [ 26 ]—“to continue to collect data until nothing new was being observed or recorded, no matter how long that takes”—was not accompanied by any term or label whatsoever.

This comparative analytic strategy (and our approach to analysis more broadly as described in strategy #7, below) is analogous to the process of reciprocal translation —a technique first introduced for meta-ethnography by Noblit and Hare [ 27 ] that has since been recognized as a common element in a variety of qualitative metasynthesis approaches [ 28 ]. Reciprocal translation, taken broadly, involves making sense of a study’s findings in terms of the findings of the other studies included in the review. In practice, it has been operationalized in different ways. Melendez-Torres and colleagues developed a typology from their review of the metasynthesis literature, describing four overlapping categories of specific operations undertaken in reciprocal translation: visual representation, key paper integration, data reduction and thematic extraction, and line-by-line coding [ 28 ]. The approaches suggested in both strategies #6 and #7, with their emphasis on constant comparison, appear to fall within the line-by-line coding category.

Generating credible and verifiable analytic interpretations

The analysis in a systematic methods overview must support its more general objective, which we suggested above is often to offer clarity and enhance collective understanding regarding a chosen methods topic. In our experience, this involves describing and interpreting the relevant literature in qualitative terms. Furthermore, any interpretative analysis required may entail reaching different levels of abstraction, depending on the more specific objectives of the review. For example, in the overview on sampling [ 18 ], we aimed to produce a comparative analysis of how multiple sampling-related topics were treated differently within and among different qualitative research traditions. To promote credibility of the review, however, not only should one seek a qualitative analytic approach that facilitates reaching varying levels of abstraction but that approach must also ensure that abstract interpretations are supported and justified by the source data and not solely the product of the analyst’s speculative thinking.

Principle #7:

Considering the qualitative nature of the analysis required in systematic methods overviews, it is important to select an analytic method whose interpretations can be verified as being consistent with the literature selected, regardless of the level of abstraction reached.

Strategy #7:

We suggest employing the constant comparative method of analysis [ 29 ] because it supports developing and verifying analytic links to the source data throughout progressively interpretive or abstract levels. In applying this approach, we advise a rigorous approach, documenting how supportive quotes or references to the original texts are carried forward in the successive steps of analysis to allow for easy verification.

The analytic approach used in the methods overview on sampling [ 18 ] comprised four explicit steps, progressing in level of abstraction—data abstraction, matrices, narrative summaries, and final analytic conclusions (Fig.  2 ). While we have positioned data abstraction as the second stage of the generic review process (prior to Analysis), above, we also considered it as an initial step of analysis in the sampling overview for several reasons. First, it involved a process of constant comparisons and iterative decision-making about the fields to add or define during development and modification of the abstraction form, through which we established the range of concepts to be addressed in the review. At the same time, abstraction involved continuous analytic decisions about what textual quotes (ranging in size from short phrases to numerous paragraphs) to record in the fields thus created. This constant comparative process was analogous to open coding in which textual data from publications was compared to conceptual fields (equivalent to codes) or to other instances of data previously abstracted when constructing definitions to optimize their fit with the overall literature as described in strategy #6. Finally, in the data abstraction step, we also recorded our first interpretive thoughts in dedicated fields, providing initial material for the more abstract analytic steps.

Summary of progressive steps of analysis used in the methods overview on sampling [ 18 ]

In the second step of the analysis, we constructed topic-specific matrices , or tables, by copying relevant quotes from abstraction forms into the appropriate cells of matrices (for the complete set of analytic matrices developed in the sampling review, see Additional file 1 (matrices 3 to 10)). Each matrix ranged from one to five pages; row headings, nested three-deep, identified the methodological tradition, author, and publication, respectively; and column headings identified the concepts, which corresponded to abstraction fields. Matrices thus allowed us to make further comparisons across methodological traditions, and between authors within a tradition. In the third step of analysis, we recorded our comparative observations as narrative summaries , in which we used illustrative quotes more sparingly. In the final step, we developed analytic conclusions based on the narrative summaries about the sampling-related concepts within each methodological tradition for which clarity, consistency, or comprehensiveness of the available guidance appeared to be lacking. Higher levels of analysis thus built logically from the lower levels, enabling us to easily verify analytic conclusions by tracing the support for claims by comparing the original text of publications reviewed.

Integrative versus interpretive methods overviews

The analytic product of systematic methods overviews is comparable to qualitative evidence syntheses, since both involve describing and interpreting the relevant literature in qualitative terms. Most qualitative synthesis approaches strive to produce new conceptual understandings that vary in level of interpretation. Dixon-Woods and colleagues [ 30 ] elaborate on a useful distinction, originating from Noblit and Hare [ 27 ], between integrative and interpretive reviews. Integrative reviews focus on summarizing available primary data and involve using largely secure and well defined concepts to do so; definitions are used from an early stage to specify categories for abstraction (or coding) of data, which in turn supports their aggregation; they do not seek as their primary focus to develop or specify new concepts, although they may achieve some theoretical or interpretive functions. For interpretive reviews, meanwhile, the main focus is to develop new concepts and theories that integrate them, with the implication that the concepts developed become fully defined towards the end of the analysis. These two forms are not completely distinct, and “every integrative synthesis will include elements of interpretation, and every interpretive synthesis will include elements of aggregation of data” [ 30 ].

The example methods overview on sampling [ 18 ] could be classified as predominantly integrative because its primary goal was to aggregate influential authors’ ideas on sampling-related concepts; there were also, however, elements of interpretive synthesis since it aimed to develop new ideas about where clarity in guidance on certain sampling-related topics is lacking, and definitions for some concepts were flexible and not fixed until late in the review. We suggest that most systematic methods overviews will be classifiable as predominantly integrative (aggregative). Nevertheless, more highly interpretive methods overviews are also quite possible—for example, when the review objective is to provide a highly critical analysis for the purpose of generating new methodological guidance. In such cases, reviewers may need to sample more deeply (see strategy #4), specifically by selecting empirical research reports (i.e., to go beyond dominant or influential ideas in the methods literature) that are likely to feature innovations or instructive lessons in employing a given method.

In this paper, we have outlined tentative guidance in the form of seven principles and strategies on how to conduct systematic methods overviews, a review type in which methods-relevant literature is systematically analyzed with the aim of offering clarity and enhancing collective understanding regarding a specific methods topic. Our proposals include strategies for delimiting the set of publications to consider, searching beyond standard bibliographic databases, searching without the availability of relevant metadata, selecting publications on purposeful conceptual grounds, defining concepts and other information to abstract iteratively, accounting for inconsistent terminology, and generating credible and verifiable analytic interpretations. We hope the suggestions proposed will be useful to others undertaking reviews on methods topics in future.

As far as we are aware, this is the first published source of concrete guidance for conducting this type of review. It is important to note that our primary objective was to initiate methodological discussion by stimulating reflection on what rigorous methods for this type of review should look like, leaving the development of more complete guidance to future work. While derived from the experience of reviewing a single qualitative methods topic, we believe the principles and strategies provided are generalizable to overviews of both qualitative and quantitative methods topics alike. However, it is expected that additional challenges and insights for conducting such reviews have yet to be defined. Thus, we propose that next steps for developing more definitive guidance should involve an attempt to collect and integrate other reviewers’ perspectives and experiences in conducting systematic methods overviews on a broad range of qualitative and quantitative methods topics. Formalized guidance and standards would improve the quality of future methods overviews, something we believe has important implications for advancing qualitative and quantitative methodology. When undertaken to a high standard, rigorous critical evaluations of the available methods guidance have significant potential to make implicit controversies explicit, and improve the clarity and precision of our understandings of problematic qualitative or quantitative methods issues.

A review process central to most types of rigorous reviews of empirical studies, which we did not explicitly address in a separate review step above, is quality appraisal . The reason we have not treated this as a separate step stems from the different objectives of the primary publications included in overviews of the methods literature (i.e., providing methodological guidance) compared to the primary publications included in the other established review types (i.e., reporting findings from single empirical studies). This is not to say that appraising quality of the methods literature is not an important concern for systematic methods overviews. Rather, appraisal is much more integral to (and difficult to separate from) the analysis step, in which we advocate appraising clarity, consistency, and comprehensiveness—the quality appraisal criteria that we suggest are appropriate for the methods literature. As a second important difference regarding appraisal, we currently advocate appraising the aforementioned aspects at the level of the literature in aggregate rather than at the level of individual publications. One reason for this is that methods guidance from individual publications generally builds on previous literature, and thus we feel that ahistorical judgments about comprehensiveness of single publications lack relevance and utility. Additionally, while different methods authors may express themselves less clearly than others, their guidance can nonetheless be highly influential and useful, and should therefore not be downgraded or ignored based on considerations of clarity—which raises questions about the alternative uses that quality appraisals of individual publications might have. Finally, legitimate variability in the perspectives that methods authors wish to emphasize, and the levels of generality at which they write about methods, makes critiquing individual publications based on the criterion of clarity a complex and potentially problematic endeavor that is beyond the scope of this paper to address. By appraising the current state of the literature at a holistic level, reviewers stand to identify important gaps in understanding that represent valuable opportunities for further methodological development.

To summarize, the principles and strategies provided here may be useful to those seeking to undertake their own systematic methods overview. Additional work is needed, however, to establish guidance that is comprehensive by comparing the experiences from conducting a variety of methods overviews on a range of methods topics. Efforts that further advance standards for systematic methods overviews have the potential to promote high-quality critical evaluations that produce conceptually clear and unified understandings of problematic methods topics, thereby accelerating the advance of research methodology.

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The systematic methods overview used as a worked example in this article (Gentles SJ, Charles C, Ploeg J, McKibbon KA: Sampling in qualitative research: insights from an overview of the methods literature. The Qual Rep 2015, 20(11):1772-1789) is available from http://nsuworks.nova.edu/tqr/vol20/iss11/5 .

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SJG wrote the first draft of this article, with CC contributing to drafting. All authors contributed to revising the manuscript. All authors except CC (deceased) approved the final draft. SJG, CC, KAB, and JP were involved in developing methods for the systematic methods overview on sampling.

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Gentles, S.J., Charles, C., Nicholas, D.B. et al. Reviewing the research methods literature: principles and strategies illustrated by a systematic overview of sampling in qualitative research. Syst Rev 5 , 172 (2016). https://doi.org/10.1186/s13643-016-0343-0

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Introduction

Scientific literature is the principal medium for communicating the results of scientific research and, as such, represents the permanent record of the collective achievements of the scientific community over time. This scientific knowledge base is composed of the individual "end products" of scientific research and discovery and continues to grow as new research builds on earlier research. This new research may add to, substantiate, modify, refine or refute existing knowledge on a specific topic. As a cycle new research and discovery in the laboratory or field is dependent on the existing scientific knowledge base which, in turn, becomes valuable when the new research is incorporated into the scientific knowledge base.

Scientific literature composing the scientific knowledge base is often divided into two basic categories:

  • Primary literature -- publications that report the results of  original  scientific research. These include journal papers, conference papers, monographic series, technical reports, theses, and dissertations.
  • Secondary literature -- publications that synthesize and condense what is known on specific topics. These include reviews, monographs, textbooks, treatises, handbooks, and manuals. These take time to produce and usually cite key "primary" publications on the topic.

Scientific Research/Publication Cycle

The following chart illustrates common steps involved in the scientific research process (inner circle), the dissemination of research results through the primary and secondary literature (outer circle), and the personal assimilation of this information resulting in new ideas and research (inner circle):

Scientific Journals, Magazines and Series

Scientific serials can be grouped into the following three categories.  Journals - Scholarly or Popular?  summarizes the differences between different types of journals and popular magazines.

Journal papers are the basic "molecular" unit of scientific knowledge base and are the most important "primary" source in the sciences. More than  80%  of the scientific research literature is published in this format. Annually 1.5 million articles are published in over 25,000 peer reviewed journals. Cumulatively there have been more than 50 million peer reviewed papers published since the first scientific journal was published in  1665 .

  • Magazines and Newsletters  -- Articles appearing in these publications tend to be popular in format and scope. They may contain news and perspectives of professional societies and environmental organizations, report on research published in scholarly journals, report on environmental problems and new political initiatives, or contain articles aimed at the layperson.
  • They are published by government agencies, universities or professional organizations. See  Natural Resources Agency Government Documents and Reports  for additional information.
  • The  series has a distinctive name. Typical names include  Bulletin ,  Special Report ,  Special Paper , Technical Report , and  Technical Paper .
  • Individual issues are consecutively numbered, e.g. Technical Paper No. 36.
  • Each issue has a distinctive author and title.
  • There is no regular publication schedule.

A typical example is:

Wheeler, W.E., R.C. Gatti, & G.A. Bartlett.(a) 1984.  Duck Breeding, Ecology and Harvest Characteristics on Grand River Marsh Wildlife Area .(b) Wisconsin Department of Natural Resources(c) Technical Bulletin(d) No. 145(e). where a=individual author; b=individual title; c=series author; d=series title; e=series number

To Find Individual Papers:  Use databases listed in  Articles and Databases  to find individual papers published in scientific journals, magazines and series. Databases typically can be searched by subject, taxonomic category, habitat, time period, chemical substance, geographic area or author. In addition the websites of many journal and magazine publishers contain searchable databases of articles published in their publications.

To Find Print and Fulltext Availability:  See the  Journal and Newspaper Finder  for specific holdings and available formats of journal, magazine and series titles available through the HSU Library. Enter the title of the publication, not the article title. In addition some series are cataloged by individual author and title in the  HSU Library Catalog . In addition directories listed in  Fulltext Journal Directories  include some fulltext journals that are not in our  Journal and Newspaper Finder .

To Find Abbrevations of Scientific Publications:  Many scientific journal and series titles are abbreviated in the literature.  Journal Title Abbreviations  lists both general abbreviation sources and more specific discipline sources in the sciences.

To Find Important Journals by Subject:  See  Journal-Ranking.com ,  Journals Ranked by Impact  (Sci-Bytes), SCImago Journal & Country Rank  and  Eigenfactor.org - Ranking and Mapping Scientific Knowledge .

Conference Papers

Papers presented at national and international conferences, symposia, and workshops are another source of "primary" scientific information . For many conferences the presented papers are eventually published in a "proceedings" or "transactions" volume. Papers with no published proceedings may be refined and reworked for formal publication in a journal. Proceedings available in the HSU Library are listed in the  HSU Library Catalog under both author (generally the name of the conference, individual editor or sponsoring organization) and title.

Many discipline databases included in  Articles and Databases  index individual conference papers by subject, taxonomic, geographic, and author. The  Conference Papers Index  and  PapersFirst  databases only index conference papers.

Theses and Dissertations

The outcome of graduate study conducted at universities is commonly a master's thesis or doctoral dissertation. In addition to the formal thesis or dissertation, research results are often communicated in other "primary" literature formats, such as the journal paper.

See  Theses and Dissertations  for how to find and acquire 1) HSU masters theses; and 2) theses and dissertations produced at other universities that are available in other libraries and on the Internet.

Scientific Monographs

Scientific monographs are book length works written by specialists for the benefit of other specialists. As defined by the  National Research Council  they attempt to "...collect, collate, analyze, integrate, and synthesize all relevant contributions to the archival literature of the scientific and engineering journals and to add original material as required". They are different from textbooks which are pedagogical works and scientific popularizations for the general public.

Monographs are listed in the  HSU Library Catalog  and in  other library catalogs .

Government Documents and Technical Reports

Scientists at federal and state government agencies conduct research that is sometimes published officially  by the government as a  government document . Other research is published in the "open" scientific literature as journal articles and other publications.

The HSU Library is an official " depository library " for federal and state govenment documents and annually receives approximately 6,000 government documents in either paper or microfiche format. In addition 80% of all recently published federal publications are available on the Internet.

Research projects conducted  for  government agencies are frequently published as  technical reports . They are usually produced in response to a specific information need with research either 1) conducted "in-house" by state or federal research labs, or 2) contracted out to universities, consulting firms, research institutes, or private industry.

Progress and final reports typically are used directly by the sponsoring agency with limited distribution beyond the organization. As a result technical report literature is sometimes called "gray literature" because of its difficulty to identify and acquire.

The format of technical reports is more flexible in organization and tends to contain more of the scientific data collected. Research first reported in a technical report may be reworked and published in other "primary" literature formats.

The  Natural Resources Agency Government Documents and Technical Reports  research guide contains further information on govenment documents and technical reports issued by federal and California State agencies, including their organization in the HSU Library and indexes to their content. The focus is on agencies responsible for managing and conducting research in natural resources.

Scientific Data

Scientific data are numerical quantities or other factual attributes derived from observation, experimentation or calculation. They are the raw material and the building block for scientific research. Through data analysis and interpretation new scientific information is generated.

The archiving of data collected and used in scientific research is important for future replication, repurposing based on new ideas or exploration of new analysis methodologies. Many funding agenices and scientific journals require authors of scientific papers to archive and share data utilized in their studies.

Data repositories archive and make data available to the scientific community. They may contain 1) data that has been collected as part of massive mission-oriented projects, e.g., atmospheric, hydrological, or oceanographic, or genomic; or 2) original data or data extracted from larger datasets that are associated with specifc published research studies.

Following are major directories of data repositories:

  • Data.gov  (United States Government) Browse or search for datasets available from US government executive agencies.
  • Data Files  (Association of College and Research Libraries. Science and Technology Section) Lists federal, state and foreign goverment data repository directories.
  • DataCite  (British Library, BioMed Central and Digital Curation Centre) Arranged alphabetically.
  • Global Change Master Directory  (Goddard Space Flight Center) Browse by broad subject area or search by keyword.
  • Open Access Directory: Data Repositories  (Graduate School of Library and Information Science, Simmons College) Arranged by broad subject.
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Literature Review: Lit Review Sources

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Where do I find information for a literature review?

Research is done by...

...by way of...

...communicated through...

...and organized in...

Types of sources for a review...

  • Primary source: Usually a report by the original researchers of a study (unfiltered sources)
  • Secondary source: Description or summary by somebody other than the original researcher, e.g. a review article (filtered sources)
  • Conceptual/theoretical: Papers concerned with description or analysis of theories or concepts associated with the topic
  • Anecdotal/opinion/clinical: Views or opinions about the subject that are not research, review or theoretical (case studies or reports from clinical settings)

A Heirarchy of research information:

Source: SUNY Downstate Medical Center. Medical Research Library of Brooklyn. Evidence Based Medicine Course. A Guide to Research Methods: The Evidence Pyramid: http://library.downstate.edu/EBM2/2100.htm

Life Cycle of Publication

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Publication Cycle of Scientific Literature

Scientific information has a ‘life cycle’ of its own… it is born as an idea, and then matures and becomes more available to the public. First it appears within the so-called ‘invisible college’ of experts in the field, discussed at conferences and symposia or posted as pre-prints for comments and corrections. Then it appears in the published literature (the primary literature), often as a journal article in a peer-reviewed journal.

Researchers can use the indexing and alerting services of the secondary literature to find out what has been published in a field. Depending on how much information is added by the indexer or abstracter, this may take a few months (though electronic publication has sped up this process). Finally, the information may appear in more popular or reference sources, sometimes called the tertiary literature.

The person beginning a literature search may take this process in reverse: using tertiary sources for general background, then going to the secondary literature to survey what has been published, following up by finding the original (primary) sources, and generating their own research Idea.

(Original content by Wade Lee-Smith)

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The Literature

The Literature refers to the collection of scholarly writings on a topic. This includes peer-reviewed articles, books, dissertations and conference papers.

  • When reviewing the literature, be sure to include major works as well as studies that respond to major works. You will want to focus on primary sources, though secondary sources can be valuable as well.

Primary Sources

The term primary source is used broadly to embody all sources that are original. P rimary sources provide first-hand information that is closest to the object of study. Primary sources vary by discipline.

  • In the natural and social sciences, original reports of research found in academic journals detailing the methodology used in the research, in-depth descriptions, and discussions of the findings are considered primary sources of information.
  • Other common examples of primary sources include speeches, letters, diaries, autobiographies, interviews, official reports, court records, artifacts, photographs, and drawings.  

Galvan, J. L. (2013). Writing literature reviews: A guide for students of the social and behavioral sciences . Glendale, CA: Pyrczak.

Secondary Sources

A secondary source is a source that provides non-original or secondhand data or information. 

  • Secondary sources are written about primary sources.
  • Research summaries reported in textbooks, magazines, and newspapers are considered secondary sources. They typically provide global descriptions of results with few details on the methodology. Other examples of secondary sources include biographies and critical studies of an author's work.

Secondary Source. (2005). In W. Paul Vogt (Ed.), Dictionary of Statistics & Methodology. (3 rd ed., p. 291). Thousand Oaks, CA: SAGE Publications, Inc.

Weidenborner, S., & Caruso, D. (1997). Writing research papers: A guide to the process . New York: St. Martin's Press.

More Examples of Primary and Secondary Sources

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various sources of research literature

The Literature Review

Primary and secondary sources, the literature review: primary and secondary sources.

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  • Primary vs secondary sources: The differences explained 

Can something be both a primary and secondary source?

Research for your literature review can be categorised as either primary or secondary in nature. The simplest definition of primary sources is either original information (such as survey data) or a first person account of an event (such as an interview transcript). Whereas secondary sources are any publshed or unpublished works that describe, summarise, analyse, evaluate, interpret or review primary source materials. Secondary sources can incorporate primary sources to support their arguments.

Ideally, good research should use a combination of both primary and secondary sources. For example, if a researcher were to investigate the introduction of a law and the impacts it had on a community, he/she might look at the transcripts of the parliamentary debates as well as the parliamentary commentary and news reporting surrounding the laws at the time. 

Examples of primary and secondary sources

Primary vs secondary sources: The differences explained

Finding primary sources

  • VU Special Collections  - The Special Collections at Victoria University Library are a valuable research resource. The Collections have strong threads of radical literature, particularly Australian Communist literature, much of which is rare or unique. Women and urban planning also feature across the Collections. There are collections that give you a picture of the people who donated them like Ray Verrills, John McLaren, Sir Zelman Cowen, and Ruth & Maurie Crow. Other collections focus on Australia's neighbours – PNG and Timor-Leste.
  • POLICY - Sharing the latest in policy knowledge and evidence, this database supports enhanced learning, collaboration and contribution.
  • Indigenous Australia  -  The Indigenous Australia database represents the collections of the Aboriginal and Torres Strait Islander Commission Library.
  • Australian Heritage Bibliography - Aboriginal and Torres Strait Islander Subset (AHB-ATSIS)  - AHB is a bibliographic database that indexes and abstracts articles from published and unpublished material on Australia's natural and cultural environment. The AHB-ATSIS subset contains records that specifically relate to the Aboriginal and Torres Strait Islander peoples.include journal articles, unpublished reports, books, videos and conference proceedings from many different sources around Australia. Emphasis is placed on reports written or commissioned by government and non-government heritage agencies throughout the country.
  • ATSIhealth  - The Aboriginal and Torres Strait Islander Health Bibliography (ATSIhealth), compiled by Neil Thomson and Natalie Weissofner at the School of Indigenous Australian Studies, Kurongkurl Katitjin, Edith Cowan University, is a bibliographic database that indexes published and unpublished material on Australian Indigenous health. Source documents include theses, unpublished articles, government reports, conference papers, abstracts, book chapters, books, discussion and working papers, and statistical documents. 
  • National Archive of Australia  - The National Archives of Australia holds the memory of our nation and keeps vital Australian Government records safe. 
  • National Library of Australia: Manuscripts  - Manuscripts collection that is wide ranging and provides rich evidence of the lives and activities of Australians who have shaped our society.
  • National Library of Australia: Printed ephemera  - The National Library has been selectively collecting Australian printed ephemera since the early 1960s as a record of Australian life and social customs, popular culture, national events, and issues of national concern.
  • National Library of Australia: Oral history and folklore - The Library’s Oral History and Folklore Collection dates back to the 1950’s and includes a rich and diverse collection of interviews and recordings with Australians from all walks of life.
  • Historic Hansard - Commonwealth of Australia parliamentary debates presented in an easy-to-read format for historians and other lovers of political speech.
  • The Old Bailey Online - A fully searchable edition of the largest body of texts detailing the lives of non-elite people ever published, containing 197,745 criminal trials held at London's central criminal court.

Whether or not a source can be considered both primary and  secondary, depends on the context. In some instances, material may act as a secondary source for one research area, and as a primary source for another. For example, Niccolò Machiavelli’s The Prince , published in 1513, is an important secondary source for any study of the various Renaissance princes in the Medici family; but the same book is also a primary source for the political thought that was characteristic of the sixteenth century because it reflects the attitudes of a person living in the 1500s.

Source: Craver, 1999, as cited in University of South Australia Library. (2021, Oct 6).  Can something be a primary and secondary source?.  University of South Australia Library. https://guides.library.unisa.edu.au/historycultural/sourcetypes

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Chapter 4: Where to Find the Literature

Learning objectives.

At the conclusion of this chapter, you will be able to:

  • Search a library catalog to locate electronic and print books.
  • Search databases to find scholarly articles, dissertations, and conference proceedings.
  • Retrieve a copy or the full text of information sources
  • Identify and locate core resources in your discipline or topic area

4.1 Overview of discovery

Discovery, or background research, is something that happens at the beginning of the research process when you are just learning about a topic. It is a search for general information to get the big picture of a topic for exploration, ideas about subtopics and context for the actual focused research you will do later. It is also a time to build a list of distinctive, broad, narrow, and related search terms.

Discovery happens again when you are ready to focus in on your research question and begin your own literature review. There are two crucial elements to discovering the literature for your review with the least amount of stress as possible: the places you look and the words you use in your search .

The places you look depend on:

  • The stage you are in your research
  • The disciplines represented in your research question
  • The importance of currency in your research topic

Review the information and publication cycles discussed in Chapter 2 to put those sources of this information in context.

The words you use will help you locate existing literature on your topic, as well as topics that may be closely related to yours. There are two categories for these words:

  • Keywords – the natural language terms we think of when we discuss and read about a topic
  • Subject terms – the assigned vocabulary for a catalog or database

The words you use during both the initial and next stage of discovery should be recorded in some way throughout the literature search process. Additional terms will come to light as you read and as your question becomes more specific. You will want to keep track of those words and terms, as they will be useful in repeating your searches in additional databases, catalogs, and other repositories. Later in this chapter, we will discuss how putting the two elements (the places we look and the words we use) together can be enhanced by the use of Boolean operators and discipline-specific thesauri.

Discovery is an iterative process. There is not a straight, bright line from beginning to end. You will go back into the literature throughout the writing of your literature review as you uncover gaps in the evidence and as additional questions arise.

various sources of research literature

4.2 Finding sources: Places to look

Let’s take some time to look at where the information sources you need for your literature review are located, indexed, and stored. At this stage, you have a general idea of your research area and have done some background searching to learn the scope and the context of your topic. You have begun collecting keywords to use in your later searching. Now, as you focus in on your literature review topic, you will take your searches to the databases and other repositories to see what the other researchers and scholars are saying about the topic.

The following resources are ordered from the more general and established information to the more recent and specific. Although it is possible to find some of these resources by searching the open web, using a search engine like Google or Google Scholar, this is not the most efficient or effective way to search for and discover research material. As a result, most of the resources described in this section are found from within academic library catalogs and databases, rather than internet search engines.

4.2.1 Finding books and ebooks

4.2.1.1 books.

Look to books for broad and general information that is useful for background research. Books are “essential guides to understanding theory and for helping you to validate the need for your study, confirm your choice of literature, and certify (or contradict) its findings.” ( Fink, 4th ed., 2014, p. 77 ). In this section, we will consider print and electronic books as well as print and electronic encyclopedias.

Most academic libraries use the Library of Congress classification system to organize their books and other resources. The Library of Congress classification system divides a library’s collection into 21 classes or categories. A specific letter of the alphabet is assigned to each class. More detailed divisions are accomplished with two and three letter combinations. Book shelves in most academic libraries are marked with a Library of Congress letter-number combination to correspond to the Library of Congress letter-number combination on the spines of library materials. This is often referred to as a call number and it is noted in the catalog record of every physical item on the library shelves. ( Bennard et al, 2014a )

The Library of Congress (LC) classification for Education (General) is L7-991, with LA, LB, LC, LD, LE, LG, LH, LJ, and LT subclasses. For example,

LB3012.2.L36 1995 Beyond the Schoolhouse Gate: Free Speech and the Inculcation of Values

In Nursing, the LC subject range is RT1-120. A book with this LC call number might look like: R121.S8 1990 Stedman’s Medical Dictionary . Areas related to nursing that are outside that range include:

R121 Medical dictionaries

R726.8 Hospice care

R858-859.7 Medical informatics

RB37 Diagnostic and laboratory tests

RB115 Nomenclature (procedural coding – CPT, ICD9)

RC69-71 Diagnosis

RC86.7 Emergency medicine

RC266 Oncology nursing

RC952-954.6 Geriatrics

RD93-98 Wound care

RD753 Orthopedic nursing

RG951 Maternal child nursing / Obstetrical nursing

RJ245 Pediatric nursing

RM216 Nutrition and diet therapy

RM301.12 Drug guides

In most libraries, there is a collection of reference material kept in a specific section. These books, consisting of encyclopedias, dictionaries, thesauri, handbooks, atlases, and other material contain useful background or overview information about topics. Ask the librarian for help in finding an appropriate reference book. Although reference material can only be used in the library, other print books will likely be in what’s called the “circulating collection,” meaning they are available to check out.

4.2.1.2 Ebooks

The library also provides access to electronic reference material. Some are subject specific and others are general reference sources. Although each resource will have a different “look” just as different print encyclopedias and dictionaries look different, each should have a search box. Most will have a table of contents for navigation within the work. Content includes pages of text in books and encyclopedias and occasionally, videos. In all cases you will be able to collect background information and search terms to use later.

North American academic libraries buy or subscribe to individual ebook titles as well as collections of ebooks. Ebooks appear on various publisher and platforms, such as Springer, Cambridge, ebrary (ProQuest), EBSCO, and Safari to name a few. Although access to these ebooks varies by platform, you can find the ebook titles your library has access to through the library catalog. You can generally read the entire book online, and you can often download single chapters or a limited number of pages. You may be able to download an entire ebook without restrictions, or you may have to ‘check it out’ for a limited period of time. Some downloads will be in PDF format, others use another type of free ebook viewing software, like ePUB. Unlike public library ebook collections, most academic library ebooks are not be downloadable to ereader devices, such as Amazon’s Kindle

4.2.1.3 The Library Catalog

In general, everything owned or licensed by a library is indexed in “the library catalog”. Although most library catalogs are now sophisticated electronic products called ‘integrated library systems’, they began as wooden card filing cabinets where researchers could look for books by author, title, or subject.

various sources of research literature

While the look and feel of current integrated library systems vary between libraries, they operate in similar ways. Most library catalogs are quickly found from a library’s home page or website. The library catalog is the quickest way to find books and ebooks on your topic.

Here are some general tips for locating books in a library catalog:

  • Use the search box generally found on a library’s home page to start a search.
  • Type a book title, author name, or subject keywords into the search box.
  • You will be directed to a results page.
  • If you click on a book title or see an option to see more details about the book, you can look at its full bibliographic record, which provides more information about the book, as well as where to find the book. Pay particular attention to subjects associated with the item, adding relevant and appropriate terms to your list of search terms for future use.
  • Look for an “Advanced Search” option near the basic or single search box
  • Publication Year
  • Call number
  • There is generally a “Format” list on the advanced search page screen. This list will give you options for limiting format to Print Books or Ebooks.
  • You can limit searches to a specific library or libraries to narrow by location or ‘search everything’ to broaden your search.

Screenshot of the OCLC WorldCat search. There are options to search "Everything," or only "Books," "DVDs," "CDs," and "Articles." There is also the option to complete an advanced search, or to "Find a library." Two taglines read "Find items in libraries near you. 2 billion items available here through a library." and "WorldCat connects you to the collections and services of more than 10,000 libraries worldwide...[link to learn more]".

OCLC WorldCat ( https://www.worldcat.org/ ) is the world’s largest network of library content and it provides another way to search for books and ebooks. For students who do not have immediate access to an academic library catalog, WorldCat is a way to search many library catalogs at once for an item and then locate a library near you that may own or subscribe to it. Whether you will be able check the item out, request it, place an interlibrary loan request for it, or have it shipped will depend on local library policy. Note that like your own library catalog, WorldCat has a single search box, an Advanced search feature, and a way to limit by format and location.

4.2.2 Finding scholarly articles

While books and ebooks provide good background information on your topic, the main body of the literature in your research area will be found in academic journals. Scholarly journals are the main forum for research publication. Unlike books and professional magazines that may comment or summarize research findings, articles in scholarly journals are written by a researcher or research team. These authors will report in detail original study findings, and will include the data used. Articles in academic journals also go through a screening or peer-review process before publication,implying a higher level of quality and reliability. For the most current, authoritative information on a topic, scholars and researchers look to the published, scholarly literature. That said,

Journals, and the articles they contain, are often quite expensive. Libraries spend a large part of their collection budget subscribing to journals in both print and online formats. You may have noticed that a Google Scholar search will provide the citation to a journal article but will not link to the full text. This happens because Google does not subscribe to journals. It only searches and retrieves freely available web content. However, libraries do subscribe to journals and have entered into agreements to share their journal and book collections with other libraries. If you are affiliated with a library as a student, staff, or faculty member, you have access to many other libraries’ resources, through a service called interlibrary loan. Do not pay the large sums required to purchase access to articles unless you do not have another way to obtain the material, and you are unable to find a substitute resource that provides the information you need. ( Bennard et al, 2014 a)

4.2.2.1 Databases

A database is an electronic system for organizing information. Journal databases are where the scholarly articles are organized and indexed for searching. Anyone with an internet connection has free access to public databases such as PubMed and ERIC. Students can also search in library-subscribed general information databases (such as EBSCO’s Academic Search Premier) or a specialized or subject specific database (for example, a ProQuest version of CINAHL for Nursing or ERIC for Education).

Library databases store and display different types of information sets than a library catalog or Google Scholar. There are different types of databases that include:

  • Indexes– with citations only
  • Abstract databases – with citations and abstracts only
  • Full text databases – with citations and the full text of articles, reports, and other materials

Library databases are often connected to each other by means of a “link resolver”, allowing different databases to “talk to each other.” For example, if you are searching an index database and discover an article you want to read in its entirety, you can click on a link resolver that takes you to another database where the full-text of the article is held. If the full-text is not available, an automated form to request the item from another library may be an option.

Why search a database instead of Google Scholar or your library catalog? Both can lead you to good articles BUT:

  • The content is wide-ranging but not comprehensive or as current as a database that may be updated daily.
  • Google Scholar doesn’t disclose its criteria for what makes the results “scholarly’ and search results often vary in quality and availability.
  • Neither gives you as much control over your search as you get in a database.

4.2.2.2 Citation searches

Another way to find additional books and articles on your topic is to mine the reference lists of books and articles you already found. By tracing literature cited in published titles, you not only add to your understanding of the scholarly conversation about your research topic but also enrich your own literature search.

A citation is a reference to an item that gives enough information for you to identify it and find it again if necessary. You can use the citations in the material you found to lead you to other resources. Generally, citations include four elements:

For example,

Figure 4.4 illustrates the different parts of a scholarly article citation, including author, date of publication, title of the article, title of the journal, volume, issue, and pages. The example shown is in APA format. Example citation item containing information in this order: Author. (Year). Article Title. Journal Title (italicized). Volume (Issue). Pages of article. The example shown following this order is: Schrecker, E. (2003). The Free speech movementL Reflections on Berkeley in the 1960s. Pacific Historical Review (italicized). 72 (4) 669-670.

For a good summary of how to read a citation for a book, book chapter, and journal article in both APA and MLA format, see this explanation   at: https://www.slideshare.net/opensunytextbooks/gathering-components-of-a-citation

4.2.3 Finding conference papers

Conference papers are often overlooked because they can be difficult to locate in full-text. Sometimes the papers from an annual proceeding are treated like an individual book, or a single special issue of a journal. Sometimes the papers from a conference are not published and must be requested from the original author. Despite publication inconsistency, conference papers may be the first place a scholar presents important findings and, as such, are relevant to your own research. Places to look for conference papers:

4.2.3.1 WorldCat

  • use keywords from the conference name (NOT the article title)
  • it often helps to leave out terms like: conference, proceedings, transactions, congresses, symposia/symposium, exposition, workshop or meeting
  • include the year of the conference
  • include the city in which the conference took place

4.2.3.2 Google Scholar

  • Search by keyword and add the word ‘conference’ and the year to your search, for example: ‘conference education 2008′

4.2.3.3 Databases

  • For Education: ERIC, limit to ‘Collected Works–Proceedings’ or ‘Speeches/Meeting papers’
  • For Nursing: CINAHL, limit to proceedings in the “Publication Type” box
  • For Education: Education Full Text, limit to ‘proceeding’ in the “Document Type” box
  • PsychInfo: limit to ‘Conference Proceedings’ in the “Record Type” Box
  • Web of Science: limit to ‘conference’

4.2.3.4 Professional Societies & Other Sponsoring Organizations

Check the web sites of the organizations that sponsor conferences. Listings of conference proceedings are often under a “Publications” or “Meetings” tab/link. The National Library of Medicine maintains a conference proceedings subject guide for health-related national and international conferences. Though many papers/proceedings are not available for free, the organization web site will often contain citations of proceedings that you can request through interlibrary loan.

4.2.4 Finding dissertations

In addition to journal articles, original research is also published in books, reports, conference proceedings, theses and dissertations. Both theses and dissertations are very detailed and comprehensive accounts of research work. Dissertations and theses are a primary source of original research and include “referencing, both in text and in the reference list, so that, in principle, any reference to the literature may be easily traced and followed up.” ( Wallace & Wray, p. 187 ). Citation searching of the reference list or bibliography in a dissertation is another method for discovering the relevant literature for your own research area. Like conference papers, they are more difficult to locate and retrieve than books and articles. Some may be available electronically in full-text at no cost. Others may only be available to the affiliates of the university or college where a degree was granted. Others are behind paywalls and can only be accessed after purchasing. Both CINAHL and ERIC index dissertations. Individual universities and institutional repositories often list dissertations held locally. Other places to look for theses and dissertations include:

Dissertations Express – search for dissertations from around the world. Search by subject or keyword, results include author, title, date, and where the degree was granted. Some are available in full-text at no cost, however most requirement payment.

EThOS – the national thesis service for the United Kingdom, managed by the British Library. It is a national aggregated record of all doctoral theses awarded by UK Higher Education institutions, providing free access to the full text of many theses for use by all researchers to further their own study.

Theses Canada – a collaborative program between Library and Archives Canada (LAC) and nearly 70 accredited Canadian universities. The collection contains both microfiche and electronic theses and dissertations that are for personal or academic research purposes.

4.3 Advanced searching

Now that you have an idea of some of the places to look for information on your research topic and the form that information takes (books, ebooks, journals, conference papers, and dissertations), it’s time to consider not only how to use the specialized resources for your discipline but how to get the most out of those resources. To do a graduate-level literature review and find everything published on your topic, advanced search and retrieval skills are needed.

4.3.1 Search Operators

Literature review research often necessitates the use of Boolean operators to combine keywords. The operators – AND, OR, and NOT — are powerful tools for searching in a database or search engine. By using a combination of terms and one or more Boolean operator, you can focus your search and narrow your search results to a more specific area than a basic keyword search allows.

Figure 4.5 is a simple diagram showing examples of how Boolean operators might be used to develop a search strategy. The examples are: solar AND energy, power OR energy, and solar NOT energy.

Boolean operators – allow you to combine your search terms using the keywords AND , OR and NOT . Look at the diagrams in Figure 4.6 to see how these terms will affect your results.

Truncation – If you use truncation (or wildcards), your search results will contain documents including variations of that term.

For example: light* will retrieve, of course, light , but also terms like: lighting , lightning , lighters and lights . Note that the truncation symbol varies depending on where you search. The most common truncation symbols are the asterisk (*) and question mark (?).

Phrase searching – Phrase searching is used to make sure your search retrieves a specific concept. For example “ durable wood products ” will retrieve more relevant documents than the same terms without quotation marks.

For a description of these more advanced search features, watch this short video tutorial on effective search strategies. ( Clark, 2016 ).

4.3.2 Finding sources in your discipline or topic area

It’s time to put these tips and your search skills to use. This is the point, if you have not done so already, to talk to a librarian. The librarian will direct you to the resources you need, including research databases to which the library subscribes, for your discipline or subject area. Literature reviews rely heavily on data from online databases, such as CINAHL for Nursing and ERIC for Education. Unfortunately, the costs to subscribe to vendor-provided products is high. Students affiliated with large university libraries that can afford to subscribe to these products will have access to many databases, while those who do not have fewer options.

Students who do not have access to subscription databases such as CINAHL or ERIC through Ebsco and ProQuest should use PubMed for Nursing at https://www.ncbi.nlm.nih.gov/pubmed/ and the public version of ERIC at https://eric.ed.gov/ for literature review research.

Although a librarian is the best resource for learning how to use a specific tool, an online tutorial on how to search PubMed may be useful and informative for those who do not have access to a librarian or a subscription database: Likewise, this document, titled “ How does the ERIC search work ,” provided by the Institute of Education Sciences provides some helpful tips for searching the public version ERIC.

4.3.3 Specialized vocabulary

One major source of search terms in a database is a specialized dictionary, or thesaurus, used to index journal articles. Thesauri provide a consistent and standardized way to retrieve information, especially when different terms are used for the same concept. According to Fink ( 2014 ), “evidence exists that using thesaurus terms produces more of the available citations than does reliance on key words…Using the appropriate subject heading will enable the reviewer to find all citations regardless of how the author uses the term.” (p. 24).

In Education and Nursing, thesauri are available. In subscription databases, as well as in PubMed and the public version of ERIC, look for the thesaurus to guide you to appropriate and relevant subject terms.

4.3.4 Citation Searching

Citation searching works best when you already have a relevant work that is on topic. From the document you identified as useful for your own literature review, you can either search citations forward or backward to gather additional resources. Cited reference searching and reference or bibliography mining are advanced search techniques that may also help generate new ideas as well as additional keywords and subject areas.

For cited reference searching, use Google Scholar or library databases such as Web of Science or Scopus. These tools trace citations forward to link to newly published books, journal articles, book chapters, and reports that were written after the document you found. Through cited reference searching, you may also locate works that have been cited numerous times, indicating what may be a seminal work in your field.

With citation mining, you will look at the references or works cited list in the resource you located to identify other relevant works. In this type of search, you will be tracing citations backward to find significant books, journal articles, book chapters, and reports that were written before the document you found. For a brief discussion about citation searching , check out this article by Hammond & Brown ( 2008 ).

The two most important finding tools you will use are a library catalog and databases. Looking for information in catalogs and databases takes practice.

Get started by setting aside some dedicated time to become familiar with the process:

  • Practice by locating one reference book and one ebook in your library catalog or WorldCat
  • Practice searching in freely available databases such as PubMed or ERIC
  • Try some of the limiters to see what each does to your search results
  • Once you find an article, what do you need to do to get it in full-text?
  • Find out how to use interlibrary loan or document delivery.

Next, complete this exercise:

  • Browse through a popular or scientific publication such as the science section of the New York Times or Scientific American . Find a short article that looks interesting and is easy to understand.
  • an article that reports on a recent study published in a scholarly journal;
  • the title of the journal;
  • the name of the author(s); and
  • an indication of when the original study appeared. Note: sometimes the source will say that the research was published in a latest issue of Science or Nature .
  • Once you find some of these facts (journal title and the authors should be sufficient), you can start to search for the primary source in a library catalog or the library’s databases.
  • Catalog search: find out if your school subscribes to a particular journal by searching for the journal by title.
  • Electronic subscription—great! It means you can access the journal right away. Once you get to the online (or electronic) version of the journal, you are given a choice of searching within this publication. An author search should be sufficient to locate the article.
  • Print subscription version—good! You can search in databases or a discovery service tool for your article by entering the journal title and the authors. Once you locate a record about the article, which will include volume and issue number, page numbers, the article title, you can go to the shelves where you will find the issue of the journal that includes your article.
  • Microform version—still good! Again, after searching databases and locating the exact information about the article, you should be able to locate the appropriate microfilm reel or microfiche. Before the widespread and easy access to online versions of materials, microforms were used to save space by preserving documents on film. Libraries are equipped with microform readers—if you need help using a reader, ask the library staff. ( Bennard et al, 2014b )

Test Yourself

Get an article.

  • Access PubMed or ERIC
  • Do a subject search, using the thesaurus (for ERIC) or MeSH terms (for PubMed)
  • Do a keyword search
  • Supplement your subject search with keywords, using advanced search tools like Boolean operators, truncation, or phrase searching
  • Limit your search by language, date of publication or PICO factor
  • Access the full text of an article you find.
  • If full text is not available, find out how to request the article through interlibrary loan

In your general topic area, do you know:

  • The core source materials?
  • The most significant theories?
  • The major issues and debates surrounding your topic area?
  • The key political, social, economic, legal, environmental, and/or technological aspects of your topic?
  • The origins of your topic?
  • The definitions for your topic?
  • How knowledge in your topic area is organized?
  • What problems or solutions have been addressed to date?
  • If you don’t know the answers to these questions, do you know how to find the answers?

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Chapter 5: The Literature Review

5.3 Acceptable sources for literature reviews

Following are a few acceptable sources for literature reviews, listed in order from what will be considered most acceptable to less acceptable sources for your literature review assignments:

  • Peer reviewed journal articles.
  • Edited academic books.
  • Articles in professional journals.
  • Statistical data from government websites.
  • Website material from professional associations (use sparingly and carefully). The following sections will explain and provide examples of these various sources.

Peer reviewed journal articles (papers)

A peer reviewed journal article is a paper that has been submitted to a scholarly journal, accepted, and published. Peer review journal papers go through a rigorous, blind review process of peer review. What this means is that two to three experts in the area of research featured in the paper have reviewed and accepted the paper for publication. The names of the author(s) who are seeking to publish the research have been removed (blind review), so as to minimize any bias towards the authors of the research (albeit, sometimes a savvy reviewer can discern who has done the research based upon previous publications, etc.). This blind review process can be long (often 12 to 18 months) and may involve many back and forth edits on the behalf of the researchers, as they work to address the edits and concerns of the peers who reviewed their paper. Often, reviewers will reject the paper for a variety of reasons, such as unclear or questionable methods, lack of contribution to the field, etc. Because peer reviewed journal articles have gone through a rigorous process of review, they are considered to be the premier source for research. Peer reviewed journal articles should serve as the foundation for your literature review.

The following link will provide more information on peer reviewed journal articles. Make sure you watch the little video on the upper left-hand side of your screen, in addition to reading the material at the following website:    http://guides.lib.jjay.cuny.edu/c.php?g=288333&p=1922599

Edited academic books

An edited academic book is a collection of scholarly scientific papers written by different authors. The works are original papers, not published elsewhere (“Edited volume,” 2018). The papers within the text also go through a process of review; however, the review is often not a blind review because the authors have been invited to contribute to the book. Consequently, edited academic books are fine to use for your literature review, but you also want to ensure that your literature review contains mostly peer reviewed journal papers.

Articles in professional journals

Articles from professional journals should be used with caution for your literature review. This is because articles in trade journals are not usually peer reviewed, even though they may appear to be. A good way to find out is to read the “About Us” section of the professional journal, which should state whether or not the papers are peer reviewed. You can also find out by Googling the name of the journal and adding “peer reviewed” to the search.

Statistical data from governmental websites

Governmental websites can be excellent sources for statistical data, e.g, Statistics Canada collects and publishes data related to the economy, society, and the environment (see https://www.statcan.gc.ca/eng/start ).

Website material from professional associations

Material from other websites can also serve as a source for statistics that you may need for your literature review. Since you want to justify the value of the research that interests you, you might make use of a professional association’s website to learn how many members they have, for example. You might want to demonstrate, as part of the introduction to your literature review, why more research on the topic of PTSD in police officers is important. You could use peer reviewed journal articles to determine the prevalence of PTSD in police officers in Canada in the last ten years, and then use the Ontario Police Officers´ Association website to determine the approximate number of police officers employed in the Province of Ontario over the last ten years. This might help you estimate how many police officers could be suffering with PTSD in Ontario. That number could potentially help to justify a research grant down the road. But again, this type of website- based material should be used with caution and sparingly.

Research Methods for the Social Sciences: An Introduction by Valerie Sheppard is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License , except where otherwise noted.

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ACAP

ACAP LEARNING RESOURCES

ACAP Pathfinder: Literature Review

  • What is a Literature Review?
  • Examples of Literature Reviews
  • The Research Question

Types of Literature

  • How to Search
  • Recording the Search
  • Reference Management
  • Evaluating the Literature

Your research question or thesis statement will inform the types of literature that will best suit the review. There are many different types literature and they come from a variety of sources. The resources described below provide you with a general outline of the types of literature available via the library. Go to the Choosing Resources page in the Information Skills guide to learn more about where and how to find these resources in the library and on the internet.

  • THEORY-BASED
  • PHILOSOPHICAL
  • STATISTICAL

Research Literature

Some edited books, journal articles, theses and government publications will employ research paradigms and methodologies to support a hypothesis. Methodologies can be broadly categorised as longitudinal, qualitative or quantitative. Many of these publications are peer-reviewed, meaning they have been checked by a panel of experts before publication. Most library databases offer a peer-reviewed checkbox which will filter search results in this way. They will also allow you to filter results according to research methodology, focus group, geographical location and much more. Research literature is an essential component of your literature review.

Theory-based Literature

Literature that is informed and tested by research, these books, articles and reference sources will attempt to explain, describe, define and provide a background or theoretical framework for a field of inquiry. These sources may include the original works of primary theorists as well as works which build upon, critique and discuss these primary sources while connecting it to the latest research. This type of literature is also an important component of any literature review.

Philosophical Literature

Information sources such as books and articles, which deal with the underlying beliefs, attitudes and concepts that form the basic assumptions or building blocks within a profession or field of study.  This kind of literature formulates critical inquiry from either an  ethical, epistemological, metaphysical or logical standpoint.  The extent to which you use philosophical literature will depend on the focus and subject matter of your review but it may be useful when constructing a background or theoretical base in your writing.

Empirical or Practice-based Literature

Statistical Reports

Grey Literature

Types of Resources

  • FILM & VIDEO
  • NEWS & MAGAZINES
  • REFERENCE SOURCES
  • CONFERENCES & THESES
  • GOVERNMENT & POLICIES

Description

Provide an overview of a subject area or of a number of related topics.  They may also include detailed information about a specific topic or topics. Search for print books using  MultiSearch .  These items may be collected from library shelves or requested from other campuses. eBooks are searchable from  MultiSearch  or  A-Z Databases  and may be read online or downloaded to any PC or device.

Use books to gather comprehensive information on a topic. In the library, you will find mostly academic, non-fiction items which may be used in your assessment tasks to sketch out an overview on a subject or to illustrate an in-depth understanding.

  • Essentials of Psychology Concepts and Applications
  • Addiction: Psychology and Treatment

Relevant Links

  • http://libguides.navitas.com/borrow
  • http://libguides.navitas.com/eresources/books

Journal publications, sometimes called periodicals or serials, contain articles which offer research, reports, reviews, letters and other papers on specific topics. They are usually published weekly, monthly, quarterly or yearly. Academic publications are often peer-reviewed and as such provide up-to-date information from authorised sources. Search for journal articles via  MultiSearch  and  A-Z  Databases . Search for journal publications using  A-Z Journals . You can also search for articles on the internet via  Google Scholar  or  Researchgate . 

Journal articles can provide you with more up-to-date information on specific aspects of a topic, and in smaller more digestible packages than books. Use journal publications to access scholarly research on a topic, often from a unique or new perspective.

  • International Journal of Clinical & Health Psychology
  • Khan, F., Chong, J., Theisen, J., Fraley, R., Young, J., & Hankin, B. (2020). Development and Change in Attachment: A Multiwave Assessment of Attachment and Its Correlates Across Childhood and Adolescence.  Journal of Personality and Social Psychology ,  118 (6), 1188–1206. https://doi.org/10.1037/pspi0000211
  • http://libguides.navitas.com/eresources/articles

Audiovisual material in the form of DVDs, podcasts, online streaming and so on, is searchable from  MultiSearch  or  A-Z Databases . Videos in the library include movies, conferences and seminars, tutorials, documentaries and much more.

AV items may be used as instructional material or gain an understanding of a topic by way of visual or concrete examples. 

  • Narrative Family Therapy
  • Waltz with Bashir
  • http://libguides.navitas.com/eresources/videos

News items are published at regular intervals and provide new information about various topics of interest to the general public. Magazines are also produced regularly and may focus on a particular subject area or cover a range of topics, again for consumption by the general public. The information within news publications and magazines are not in themselves scholarly works but may refer to academic sources. These sources can be found by searching  MultiSearch  or  A-Z Databases

To access recent or new information about current affairs, social, economic or political issues which provide an overview or introduction in digestible and readable packages.  While not scholarly information, these resources may be required for use in particular assessment tasks or point towards recent research in a particular field. 

  • Australia targeted in cyber crime increase
  • New Scientist
  • Search for news on Google

Reference items such as dictionaries, encyclopaedias, handbooks and industry standards provide an overview of a subject area, or include specific definitions, technical or practical information. They are searchable via  MultiSearch  and  A-Z Databases . Reference works at ACAP cover a range of topics including but not limited to sociology, social work and philosophy, psychology, counselling and mental illness, legal materials and policies, diagnoses, drug overviews, care planning and best practices for healthcare workers.

Useful for a broad understanding of a topic, theory or theorist or for assessment tasks which require technical or practical information about a particular industry or field of inquiry. 

  • Evidence-Based Policy
  • Diagnostic and statistical manual of mental disorders : DSM-5

A website is a set of related and interlinked pages which are hosted on the World Wide Web (WWW). A webpage refers to the individual pages contained within these sites. To search the WWW, download an internet browser (we recommend Google Chrome) and use a search engine such as Google to find content.

The websites of particular institutions and government departments may be useful for your assessment tasks. You might also want to look at scholarly sites, such as Google Scholar, Researchgate, State Libraries, academic publishers and journal indexing services, to find the most scholarly information on the Web. Links recommended by the library can be found on the  Useful Websites  page. 

  • Google Scholar
  • Dulwich Centre Resources

Conference papers are presented at conferences which are usually themed around a specific subject area or set of related topics and presented as a collection of proceedings. Some papers may be peer-reviewed and are searchable from  MultiSearch , within  journal databases ,  Dissertation Express  or via  Libraries Australia Trove database . A thesis or dissertation involves personal research, written by a candidate for an advanced university degree. Theses are also searchable from  MultiSearch ,  Trove , or within individual academic institutional repositories and indexing databases such as  PQDT Open ,  NDLTD ,  CORE  and  DART .

Conference proceedings and theses can provide you with an in-depth look at some of the latest research on specific aspects of a topic.

  • Counselor education: A personal growth & personal development experience
  • Awareness of memory deficits in Parkinson’s disease
  • http://libguides.navitas.com/ill

Legal resources include documents such as, but not limited to Bills, Acts, regulations, statutory laws, by-laws, proceedings of Parliament, legal cases and tribunal decisions. Some of these resources may be found by searching  MultiSearch , in databases such as  AustLII  or  JADE  or within legislative sites for individual states and territories. You will also find cases and tribunal decisions on the websites of regulatory authorities such as  AHPRA .

Use these information sources when you need to refer to current laws, records, cases and decisions in your assessment tasks.   

  • AustLII Cases & Legislation
  • Library Resources for Criminology & Justice: Law & Legislation

Government policies, reports, gazettes, media releases and parliamentary publications such as Hansards, are available from various websites here in Australia.  You can also search Google to find individual publications.  MultiSearch  and  journal  databases  will include some government papers and reports in search results.  However, you should also directly consult  federal  and  state  departments and agencies, Libraries Australia  GovPubs,  the  Analysis and Policy Observatory  and State and  Federal  Parliamentary libraries. 

Use these sources in your assessment tasks to access up-to-date and authoritative information on subject areas which may be affected by Federal or State government.

  • Domestic and family violence and parenting: mixed method insights into impact and support needs - final report
  • National Statement on Ethical Conduct in Human Research

Statistical reports and data from sites such as the  Australian Bureau of Statistics  gather information for a particular field of research or to report on the views and habits of the population. Data collection may be performed via interviews, questionnaires, surveys, censuses and so on. You'll also be able to search for and access statistical information using  MultiSearch  and  journal databases . Other important sites for statistics include the  Australian Institute of Family Studies ,  Australian Institute of Health & Welfare  and  HILDA .

An important part of the research in any field of study, statistical reporting and datasets are useful for description, analysis and comparison in your assessment tasks.

  • 4329.0.00.003 - Patterns of Use of Mental Health Services and Prescription Medications, 2011
  • Parent-child contact after separation
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  • Next: How to Search >>
  • Last Updated: Sep 13, 2023 10:53 AM
  • URL: https://libguides.navitas.com/literature-review

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Scholarly Literature Types

Types of scholarly literature, non-formally published substantive literature.

  • Acknowledgements
  • Peer Review This link opens in a new window
  • Examples of Academic Sources
  • Qualitative vs Quantitative Research
  • Anatomy of a Scholarly Article

You will encounter many types of articles and it is important to distinguish between these different categories of scholarly literature. Keep in mind the following definitions.

Peer-reviewed (or refereed):  Refers to articles that have undergone a rigorous review process, often including revisions to the original manuscript, by peers in their discipline, before publication in a scholarly journal. This can include empirical studies, review articles, meta-analyses among others.

Empirical study (or primary article): An empirical study is one that aims to gain new knowledge on a topic through direct or indirect observation and research. These include quantitative or qualitative data and analysis. In science, an empirical article will often include the following sections: Introduction, Methods, Results, and Discussion.

Review article:  In the scientific literature, this is a type of article that provides a synthesis of existing research on a particular topic. These are useful when you want to get an idea of a body of research that you are not yet familiar with. It differs from a systematic review in that it does not aim to capture ALL of the research on a particular topic.

Systematic review:  This is a methodical and thorough literature review focused on a particular research question. It's aim is to identify and synthesize all of the scholarly research on a particular topic in an unbiased, reproducible way to provide evidence for practice and policy-making. It may involve a meta-analysis (see below). 

Meta-analysis:  This is a type of research study that combines or contrasts data from different independent studies in a new analysis in order to strengthen the understanding of a particular topic. There are many methods, some complex, applied to performing this type of analysis.

What is Grey Literature?

Grey literature is literature produced by individuals or organizations outside of commercial and/or academic publishers. This type of non-formally published substantive information (often not formally peer-reviewed; especially important in all kinds of sciences) can include information such:

  • theses and dissertations
  • technical reports 
  • working papers 
  • government reports
  • evaluation and think tank reports and resources
  • conference proceedings, papers and posters
  • publications from NGOs, INGOs, think tanks and policy institutes
  • unpublished clinical trials
  • and much more

The sources you select will be informed by your research question and field of study, but should likely include, at a minimum, theses and dissertations.

Why Search the Gray Literature?

Most of gray literature is considered less prestigious, reliable, and "official" than publication in a peer-reviewed journal. But they are still fully legitimate avenues of publication. Often they are used to publicize early findings, before a study is entirely complete. Or, in the case of theses, they are published as a condition of receiving an advanced degree. Government technical reports are issued either by agencies that do scientific research themselves or else by a lab that has received government funding. Increasingly, such labs may be required to publish technical reports as a condition of receiving such funding. Gray literature may be cited like any other paper although with the caveat mentioned before that it is considered less "official" and reliable than peer-reviewed scientific papers.

When doing evidence synthesis, it's important because the intent is to synthesize  all available evidence  that is applicable to your research question. There is a strong bias in scientific publishing toward publishing studies that show some sort of significant effect. Meanwhile, many studies and trials that show no effect end up going unpublished. But knowing that an intervention had no effect is just as important as knowing that it did have an effect when it comes to making decisions for practice and policy-making. While not peer-reviewed, gray literature represents a valuable body of information that is critical to consider when synthesizing and evaluating all available evidence.

The guide is based on the Cornell University Library Tutorial: Scholarly Literature Types.

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  • Last Updated: Sep 13, 2023 5:23 PM
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How to Synthesize Written Information from Multiple Sources

Shona McCombes

Content Manager

B.A., English Literature, University of Glasgow

Shona McCombes is the content manager at Scribbr, Netherlands.

Learn about our Editorial Process

Saul Mcleod, PhD

Editor-in-Chief for Simply Psychology

BSc (Hons) Psychology, MRes, PhD, University of Manchester

Saul Mcleod, Ph.D., is a qualified psychology teacher with over 18 years experience of working in further and higher education. He has been published in peer-reviewed journals, including the Journal of Clinical Psychology.

On This Page:

When you write a literature review or essay, you have to go beyond just summarizing the articles you’ve read – you need to synthesize the literature to show how it all fits together (and how your own research fits in).

Synthesizing simply means combining. Instead of summarizing the main points of each source in turn, you put together the ideas and findings of multiple sources in order to make an overall point.

At the most basic level, this involves looking for similarities and differences between your sources. Your synthesis should show the reader where the sources overlap and where they diverge.

Unsynthesized Example

Franz (2008) studied undergraduate online students. He looked at 17 females and 18 males and found that none of them liked APA. According to Franz, the evidence suggested that all students are reluctant to learn citations style. Perez (2010) also studies undergraduate students. She looked at 42 females and 50 males and found that males were significantly more inclined to use citation software ( p < .05). Findings suggest that females might graduate sooner. Goldstein (2012) looked at British undergraduates. Among a sample of 50, all females, all confident in their abilities to cite and were eager to write their dissertations.

Synthesized Example

Studies of undergraduate students reveal conflicting conclusions regarding relationships between advanced scholarly study and citation efficacy. Although Franz (2008) found that no participants enjoyed learning citation style, Goldstein (2012) determined in a larger study that all participants watched felt comfortable citing sources, suggesting that variables among participant and control group populations must be examined more closely. Although Perez (2010) expanded on Franz’s original study with a larger, more diverse sample…

Step 1: Organize your sources

After collecting the relevant literature, you’ve got a lot of information to work through, and no clear idea of how it all fits together.

Before you can start writing, you need to organize your notes in a way that allows you to see the relationships between sources.

One way to begin synthesizing the literature is to put your notes into a table. Depending on your topic and the type of literature you’re dealing with, there are a couple of different ways you can organize this.

Summary table

A summary table collates the key points of each source under consistent headings. This is a good approach if your sources tend to have a similar structure – for instance, if they’re all empirical papers.

Each row in the table lists one source, and each column identifies a specific part of the source. You can decide which headings to include based on what’s most relevant to the literature you’re dealing with.

For example, you might include columns for things like aims, methods, variables, population, sample size, and conclusion.

For each study, you briefly summarize each of these aspects. You can also include columns for your own evaluation and analysis.

summary table for synthesizing the literature

The summary table gives you a quick overview of the key points of each source. This allows you to group sources by relevant similarities, as well as noticing important differences or contradictions in their findings.

Synthesis matrix

A synthesis matrix is useful when your sources are more varied in their purpose and structure – for example, when you’re dealing with books and essays making various different arguments about a topic.

Each column in the table lists one source. Each row is labeled with a specific concept, topic or theme that recurs across all or most of the sources.

Then, for each source, you summarize the main points or arguments related to the theme.

synthesis matrix

The purposes of the table is to identify the common points that connect the sources, as well as identifying points where they diverge or disagree.

Step 2: Outline your structure

Now you should have a clear overview of the main connections and differences between the sources you’ve read. Next, you need to decide how you’ll group them together and the order in which you’ll discuss them.

For shorter papers, your outline can just identify the focus of each paragraph; for longer papers, you might want to divide it into sections with headings.

There are a few different approaches you can take to help you structure your synthesis.

If your sources cover a broad time period, and you found patterns in how researchers approached the topic over time, you can organize your discussion chronologically .

That doesn’t mean you just summarize each paper in chronological order; instead, you should group articles into time periods and identify what they have in common, as well as signalling important turning points or developments in the literature.

If the literature covers various different topics, you can organize it thematically .

That means that each paragraph or section focuses on a specific theme and explains how that theme is approached in the literature.

synthesizing the literature using themes

Source Used with Permission: The Chicago School

If you’re drawing on literature from various different fields or they use a wide variety of research methods, you can organize your sources methodologically .

That means grouping together studies based on the type of research they did and discussing the findings that emerged from each method.

If your topic involves a debate between different schools of thought, you can organize it theoretically .

That means comparing the different theories that have been developed and grouping together papers based on the position or perspective they take on the topic, as well as evaluating which arguments are most convincing.

Step 3: Write paragraphs with topic sentences

What sets a synthesis apart from a summary is that it combines various sources. The easiest way to think about this is that each paragraph should discuss a few different sources, and you should be able to condense the overall point of the paragraph into one sentence.

This is called a topic sentence , and it usually appears at the start of the paragraph. The topic sentence signals what the whole paragraph is about; every sentence in the paragraph should be clearly related to it.

A topic sentence can be a simple summary of the paragraph’s content:

“Early research on [x] focused heavily on [y].”

For an effective synthesis, you can use topic sentences to link back to the previous paragraph, highlighting a point of debate or critique:

“Several scholars have pointed out the flaws in this approach.” “While recent research has attempted to address the problem, many of these studies have methodological flaws that limit their validity.”

By using topic sentences, you can ensure that your paragraphs are coherent and clearly show the connections between the articles you are discussing.

As you write your paragraphs, avoid quoting directly from sources: use your own words to explain the commonalities and differences that you found in the literature.

Don’t try to cover every single point from every single source – the key to synthesizing is to extract the most important and relevant information and combine it to give your reader an overall picture of the state of knowledge on your topic.

Step 4: Revise, edit and proofread

Like any other piece of academic writing, synthesizing literature doesn’t happen all in one go – it involves redrafting, revising, editing and proofreading your work.

Checklist for Synthesis

  •   Do I introduce the paragraph with a clear, focused topic sentence?
  •   Do I discuss more than one source in the paragraph?
  •   Do I mention only the most relevant findings, rather than describing every part of the studies?
  •   Do I discuss the similarities or differences between the sources, rather than summarizing each source in turn?
  •   Do I put the findings or arguments of the sources in my own words?
  •   Is the paragraph organized around a single idea?
  •   Is the paragraph directly relevant to my research question or topic?
  •   Is there a logical transition from this paragraph to the next one?

Further Information

How to Synthesise: a Step-by-Step Approach

Help…I”ve Been Asked to Synthesize!

Learn how to Synthesise (combine information from sources)

How to write a Psychology Essay

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Consumer Awareness of Plastic: an Overview of Different Research Areas

  • Original Paper
  • Published: 25 March 2023
  • Volume 3 , pages 2083–2107, ( 2023 )

Cite this article

  • Fabiula Danielli Bastos de Sousa   ORCID: orcid.org/0000-0002-5776-2247 1 , 2  

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Plastic makes our society more practical and safer. It is hard to consider eliminating plastic in some sectors, such as the medical field. However, after use, plastic waste becomes a global problem without precedents, and when not properly disposed of, it can cause several socio-environmental problems. Some possible solutions are recycling, the circular economy, proper waste management, and consumer awareness. Consumers play a crucial role in preventing problems caused by plastic. In this work, consumer awareness of plastic is discussed according to the point of view of the research areas—environmental science, engineering, and materials science—based on the analysis of the main authors’ keywords obtained in a literature search in the Scopus database. Bibliometrix analyzed the Scopus search results. The results showed that each area presents different concerns and priorities. The current scenario, including the main hotspots, trends, emerging topics, and deficiencies, was obtained. On the contrary, the concerns from the literature and those of the daily lives of consumers do not seem to fit in, which creates a gap. By reducing this gap, the distance between consumers awareness and their behavior will be smaller.

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Avoid common mistakes on your manuscript.

Introduction

The correct management of plastic waste is a complex and delicate task. Several characters are involved but the consumer has a relevant role, being responsible for segregating and discarding all the waste they produce.

The greater the economic prosperity of a region is, the greater its municipal solid waste (MSW) composition complexity [ 1 ]. More available products and services for citizens occur as countries and cities become more prosperous and more populated [ 2 ]. In high-income countries and cities, packing wastes, especially plastics, are predominant among all the waste produced [ 3 ]. Consequently, the higher the MSW composition complexity, the greater the difficulty of managing it, especially the correct management of plastic. Plastic is ubiquitous in our lives and modern society, being a massive increase in the production of fibers and resins, from 2 Mt in 1950 to around 380 Mt in 2015 [ 4 ].

Plastic plays a unique socioeconomic role. Worldwide, thousands of jobs are generated, whether in the production or recycling of plastic [ 5 ]. Thus, in addition to contributing to the economy, it plays a tremendous social role. Employment can be defined as a source of income and also a link of its identity over individual attributions introduced by its achievement of the task [ 6 ]. In addition, employment means social integration, allowing contact among people, insertion, and the feeling of belonging to a group [ 7 ].

However, even with a tremendously positive influence on society [ 5 ], plastic pollution outperforms it, making plastic a major polluter. Over the years, people have accompanied a significant increase in the pollution of water bodies by plastic, reaching up to 53 Mt per year by 2030 [ 8 ]. According to Geyer et al. [ 4 ], around 6300 Mt of plastic waste had been generated up to 2015, being recycled only about 9% of this amount.

Even with legal procedures, regulations, and levies regarding the reduction of single-use plastic [ 9 , 10 , 11 , 12 , 13 , 14 ], knowing that the circular economy is crucial to reduce plastic pollution [ 15 , 16 ], and knowing all the problems that plastic can cause when improperly disposed of, some consumers do not fulfill their role regarding the correct segregation and the final disposal of plastic waste that they produce. Some authors consider consumers as a primary source of plastic pollution [ 17 ] due to their lack of awareness or contribution to dealing with plastic. Besides, consumers may not want to put information into practice on individual actions relative to environmental and economic benefits [ 17 ].

Bibliometric analysis is an important instrument used to have an overview of different knowledge areas. Using specific software programs, the data of the publications collected from a search in a given database can be analyzed from a quantitative point of view. Among the possible data to be analyzed, the investigation of the keywords is essential to determine the research trend, identify gaps in the discussion concerning a given subject/research area, and identify the fields that can be interesting as future research areas [ 18 ]. The obtained results are relevant to influence new researchers to achieve progress in a given research area.

Considering the distinct role of consumers in the correct management of plastic waste and all the consequences that its incorrect management is likely to result in, consumer awareness of plastic was discussed, according to the literature of the last two decades. The analysis was based on the analysis of the main authors’ keywords obtained from a search in the Scopus database. Deepening the discussion, the point of view of the research areas—environmental science, engineering, and materials science—was also studied. The primary purpose was to comprehend the contribution of each area in developing consumer awareness of plastic. The results have shown that each area has different concerns and priorities. The current scenario was obtained by including the main hotspots, trends, emerging topics, and deficiencies.

Literature Review

Awareness is the knowledge that something exists or the understanding of a situation or subject based on information or experience [ 19 ]. Thus, within the scope of this work, although consumers know the problems that the incorrect disposal of plastic waste causes and the possible actions to mitigate existing problems, they do not collaborate positively.

Thomas [ 20 ] categorized four dynamic and ever-changing forms of non-recognition or unawareness, trying to elucidate why pollution is ignored:

Recognized unawareness: An individual perceives that pollution can cause negative effects but believes that the information is insufficient.

False awareness: An individual trusts to have all the information and that it is accessible, even having insufficient, outdated, or misunderstood information.

Deliberate unawareness: People do not consider as significant an environmental topic and then do not search for further information on it.

Concealed awareness: Information is omitted by an actor who is unable or does not feel like sharing it with others. There can be financial motivation issues or a benevolent effort to secure the public.

In the circular economy, waste is a raw material. Waste is a resource continually circulated within the economy [ 21 ]. It is a valuable material. The consumer is responsible for making available correctly the recyclable waste they produce for selective collection. The consumer is responsible for reintroducing the plastic waste to the cycle again (Fig.  1 item 3). Then, the plastic waste is collected, separated, and washed, i. e., it is prepared for recycling (Fig.  1 item 4). Plastic is recycled (Fig.  1 item 5), becoming a raw material for producing new items. In the sequence, it is transformed into other items (Fig.  1 item 1). After, the items made of recycled plastic go to consumer markets (Fig.  1 item 2), and then, consumed again (Fig.  1 item 3), closing the cycle (considering the mechanical recycling). This cycle constitutes the circular economy (Fig.  1 ). However, the role of the consumer regarding plastic does not end at that point—it goes far beyond. Some authors [ 22 ] have identified 14 critical roles of the consumers in reducing plastic pollutants, as follows:

Support plastic-free brands and supermarkets;

Take initiatives to limit plastic littering;

Ensure proximity of waste disposal bins;

Contribute to municipal services;

Comply with regulations;

Demand for sustainable and biodegradable product options;

Reduce reliance on single-use of plastic;

Plan green purchasing;

Positive attitude towards responsible consumption and reuse of plastic;

Clear perception of the adverse environmental effects of plastic pollution;

Emphasize proper recycling practices;

Conversion of plastic source into a resource;

Promote green packaging preferences;

Motivate to opt for the green lifestyle.

figure 1

Summarized circular economy of plastic. The photo in the center shows a Magellanic Penguin found dead with a face mask in its stomach. The use of the photo was authorized by Instituto Argonauta [ 23 ]

The lack of consumer awareness plays a crucial role in recycling rates. In some countries, such as Brazil, recycling rates are meager—only about 4%. Even worse, it causes plastic pollution, mainly in water bodies (as aforementioned), which causes negative impacts on the environment, fauna, and human health.

Plastic is found in several sizes in different water bodies around the globe, but the most common are microplastics [ 24 , 25 , 26 , 27 , 28 , 29 ], fragments of polymeric origin with dimensions between 1 and 1000 μm [ 30 ]. Some products, such as wet wipes [ 27 ], sanitary towels [ 27 ], and face masks [ 31 , 32 , 33 ], are sources of microplastics in water bodies when improperly disposed of.

Microplastics in water bodies damage different organisms as they cannot distinguish them from food [ 34 ]. The accumulation of plastic in their organisms hinders digestion and the absorption of nutrients, reducing the reserve of energy available and leading to premature death [ 35 ]. As a shocking example, news addressed a Magellanic Penguin found dead on a beach in the city of São Sebastião, on the north coast of São Paulo (Brazil). During its necropsy, a face mask (made of plastic) was found in its stomach (photo in the center of Fig.  1 ), the cause of its death [ 36 ].

Microplastics can be easily ingested by aquatic animals and by humans due to their small size. Additionally, microplastics can adsorb different contaminants, increasing their toxicity. It is estimated that humans ingest up to 5 g of microplastics per week [ 37 ]. The literature points to inflammation as the major impact of microplastics on human health [ 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 ]. Recently, microplastics were detected in breast milk for the first time [ 52 ].

Methodology

The methodology used in this work is described by de Sousa [ 53 ]. The bibliographic data inputs were obtained through a Scopus search on 12 August 2021. The keywords used were (consumer*) AND (awareness OR consciousness) AND (plastic* OR polymer*). Reviews and articles in English were considered from 2001 to 2020.

From Scopus, a scopus.bib file containing the data was taken, and a bibliometric analysis using the Bibliometrix (an R-package) was performed.

Next, from the Scopus search, the results obtained were limited to environmental science, engineering, and materials science research areas. For each area investigated, a scopus.bib file with the data was recorded and used to analyze the authors’ keywords.

The word cloud contains the 50 most frequent authors’ keywords. Five keywords per year with a minimum frequency of occurrence of 3 were analyzed for the evolution of the main terms.

Results and Discussion

The Scopus search obtained a total of 191 publications, with 156 articles and 35 reviews in English. The number of publications per year and area is presented in Fig.  2 .

figure 2

Number of publications per year ( a ) and per area ( b )

The results show a growth in the number of publications over the period, with an annual growth rate of 15.39% (according to Bibliometrix). Even with a trend of increase in this figure, the number of annual publications is still low given the great relevance of the subject, and also demonstrates a real possibility of growth and improvement in the area, with ample space for research and development [ 54 ].

By analyzing the authors’ keywords, it is possible to obtain a panorama of the research field [ 55 ], as well as the hotspots and future trends. Authors use keywords to communicate their wishes to readers and the scientific community [ 56 ]. Some authors [ 54 ] explain that “keywords are the core of the paper, which indicates the research direction of the field by abstracting and summarizing the research content of the academic paper.” Given the importance of analyzing the authors’ keywords, they will be discussed in the present work.

The research area of consumer awareness of plastic (encompassing all the involved research areas) will be analyzed in the sequence.

All the Research Areas

From the 191 publications, a total of 720 authors’ keywords were obtained. The most relevant are as follows (number of occurrences in parenthesis): waste management (9), recycling (8), sustainability (7), plastic waste (6), packaging (5), consumer behavior (4), microplastics (4), pollution (4), and biopolymers (3). These keywords are hotspots concerning consumer awareness of plastic, especially waste management [ 57 , 58 ].

Figure  3 presents the word cloud containing the 50 more frequently observed authors’ keywords in the results of the Scopus search about consumer awareness of plastic and the trending topic. The word cloud analysis can provide an overview of the current literature about consumer awareness of plastic. The size of the letters represents the frequency of the keyword. The word cloud contains the authors’ keywords that are more relevant in the field. Therefore, as a panorama is provided, the discussion can be deepened.

figure 3

( a ) Word cloud containing the 50 principal authors’ keywords. ( b ) Evolution of the main terms

Based on the authors’ keywords with the highest frequency and the word cloud, a concern from the literature about the problems that plastic (“plastic waste,” “packaging”) can cause/aggravate in the environment can be observed (“pollution,” “microplastics”), as well as the possible solutions to mitigate them (“consumer behavior,” “waste management,” “recycling,” and use of “biopolymers” and “biodegradable polymers”). This result also demonstrates the vital role of consumers in the plastics recycling chain through their pro-environmental behavior (“consumer behavior”).

Some possibilities to mitigate plastic pollution include the correct “management of plastic,” “recycling,”  “levies,” and “consumer behavior.”

Other concerns depicted in the word cloud are the management of “e-waste” [ 59 ] and “food safety” [ 24 , 58 ].

Single-use plastic is a massive concern in consumer awareness of plastic research. Around 49% of the global production of plastic is constituted by single-use items [ 60 ]. The point to be considered is that single-use plastic has a very short lifetime, being discarded just after use and consequently becoming responsible for enhancing the environmental damages and concerns caused by plastic waste. According to Forbes [ 61 ], around 160,000 plastic bags are used per second worldwide, and only less than 3% of this amount is effectively recycled. The literature [ 62 ] describes a more negative perception towards single-use plastic and relatively high awareness of the environmental impacts they cause, as observed in the word cloud due to the keywords “plastic straws” and “plastic bags.” Negative discernments of single-use plastic consumption are linked to higher levels of environmental awareness [ 63 , 64 ]. On the other hand, even knowing the negative impact of plastic, some consumers still use them indistinctly [ 65 ].

According to Winton et al. [ 64 ], the most found macroplastics in freshwater environments in Europe are single-use short-term food acquisitions. Single-use plastics contribute to 60–95% of global marine plastic pollution [ 9 ]. So, abolishing all single-use products can effectively protect the environment and the world’s oceans [ 63 ].

Consumers can decide to reduce single-use plastic bags (SUPBs) in their daily life and engage in pro-environmental behavior [ 63 ]. In Chile, an informal and uncoordinated alliance of different sectors, including science, media, the general public, government agencies, schools, and universities, promoted the demise of SUPBs [ 63 ].

The literature points out to the circular economy and recycling as possible solutions for plastic waste management. The commitment of consumers, government, and companies (through the extended producer responsibility [ 66 ]), as part of the circular economy, is essential for reducing/solving the massive problem of plastic management since each sector is co-responsible for the environmental problems generated by plastic [ 55 ].

According to Fig.  3 b, the evolution of the main terms can be visualized. Some terms have been kept in evidence in the literature for an extended period, such as “mechanical properties,” “consumer behavior,” and “food safety.” However, they have lost their evidence to other terms, such as “packaging,” “sustainability,” “marine debris,” “microplastics,” and “plastic waste.” The terms with the highest frequency are the most popular authors’ keywords, as depicted before. The term “waste management” has been kept in evidence from 2012 to 2020. It has the highest frequency, corroborating Fig.  3 a. The terms with the highest frequencies, as mentioned previously, are currently in evidence, being considered hotspots in the research field of consumer awareness of plastic.

Regarding the authors’ keywords, 584 are from articles, and 136 are from reviews.

Based on the analysis of the authors’ keywords, emerging topics and trends are obtained. Trends or, in other words, subjects highly investigated, are present in reviews, whereas emerging topics are present in articles [ 67 ].

Table  1 presents the most frequent authors’ keywords in articles and reviews. The minimum number of occurrences for each keyword is 2. The keywords were separated into the following categories: actor, source, problem, mitigation, consequence, and policy. The main problem was plastic pollution (“microplastics,” “marine debris,” etc.). The actor is responsible for the problem, i.e., “consumer behavior.” The sources are the ones that produce plastic pollution, such as “plastic waste.” The consequences are the effects of plastic pollution. Mitigations lessen the consequences of plastic pollution. Furthermore, a policy is a rule to be followed by the population, such as a ban on a given plastic item. Plastic packages act as a barrier, protecting food against damage (food safety), and reducing food waste. However, some additives in the plastic can migrate to food in contact with the package, resulting in health impacts. So, the authors’ keywords “food safety,” “food contact material,” and “food waste” were categorized into a consequence.

Table  1 shows that reviews focus on human health impacts caused by plastic pollution, some sources, consequences, and mitigations. Conversely, in articles, authors focus on the mitigations of plastic pollution.

Some of the most frequent authors’ keywords are from articles (Fig.  3 a); so, a high contribution of articles in the current literature can be observed, such as the concerns expressed by authors considered emerging trends [ 67 ].

Directions can be obtained through the divergences among the keywords in articles and reviews [ 67 ]. Based on Table  1 , some mismatches are observed, such as actors, mitigations, and policies. These discrepancies are considered deficiencies on which the literature should be focused. So, themes contemplated in these categories can be attractive for future research. Thus, future works can focus on the abovementioned themes to mitigate plastic pollution caused mainly by the need for more consumer awareness [ 68 , 69 ].

“A large proportion of the plastic waste is caused due to consumerism” [ 68 ]. In general, the incorrect disposal of plastic waste is caused, in large part, by the lack of awareness of consumers or, in other words, by the “throwaway behavior” of consumers [ 68 ].

Consumer awareness can change consumer behavior. However, if changes do not happen, negative consequences can occur due to wrong political and entrepreneurial strategies because of a lack of information about consumer awareness [ 70 ]. Based on this, consumer awareness of plastic must be understood in depth to achieve a change in consumer habits for the common good. Most studies focus on environmental concerns and the disposition of consumers to purchase alternative products [ 68 , 71 ]. On the other hand, consumer awareness of plastic does not involve only environmental aspects, evidenced by the numerous research areas with publications on the subject (Fig.  2 b). Literature is constructed from the contribution of many different knowledge areas.

To better understand the interests and concerns of some of the different research areas, the literature on the areas of environmental science, engineering, and materials science (some of the areas with the highest number of publications) will be briefly analyzed, focusing on the analysis of the authors’ keywords of these research areas. Based on this, the contribution of each area in developing consumer awareness about plastic can be understood.

Environmental Science

The Scopus search about consumer awareness of plastic limited to the environmental science area (68 publications—60 articles and 8 reviews) obtained a total of 286 authors’ keywords. The most relevant are as follows (number of occurrences in parenthesis): waste management (7), plastic waste (5), recycling (5), consumer behavior (4), microplastics (4), marine debris (3), plastic bag levy (3), plastic pollution (3), and pollution (3).

The word cloud containing the 50 more frequently observed authors’ keywords in the publications of the environmental science area is shown in Fig.  4 .

figure 4

Word cloud containing the 50 main authors’ keywords of the environmental science area

The role of consumers is evidenced through the keywords “awareness of consequences” [ 72 ], “consumer preferences” [ 73 , 74 ], “attitude,” “theory of planned behavior” [ 75 ], “beliefs,” “behavior-based solutions,” “behavior change” [ 76 ], “anti-consumption behavior” [ 77 ], “awareness” [ 68 , 78 ], “choice experiment” [ 74 ], “behavior,” “consumer behavior” [ 62 , 64 ], “pro-environmental behavior,” and “willingness to pay” [ 79 ]. Some keywords present a minor frequency. The high number of keywords concerning the behavior of consumers shows that the environmental science area focuses on consumers. Their behavior and consumption are responsible for environmental problems caused/aggravated by plastic. As aforementioned, consumers also play an essential role in correctly managing plastic and its recycling [ 75 ] (Fig.  1 ).

Other possible solutions to mitigate the problems that plastic can cause are posed by the environmental science area, such as the use of “bioplastic bottles,” “bio-based packaging” [ 80 ], “biodegradable plastic bottles” (in substitution for conventional plastic bottles [ 81 ]), “bio-based plastic,” the correct “management of plastic waste” [ 63 ], “recycling” [ 75 ], and “plastic bag levies” [ 77 , 79 , 82 ].

Habits, norms, and situational factors predict the behavior of consumers. Despite a pronounced awareness of the associated problems that plastic can cause, consumers keep on appreciating and using it [ 65 ]. In Taiwan, some authors [ 1 ] demonstrated that the plastic and glass waste generation rate declined when economic activities expanded, mainly due to the strict enforcement of recycling policies accompanied by marketing campaigns encouraging recycling and enhancing the green awareness of consumers. Accordingly, an opportunity to increase consumer awareness is to encourage the opening of zero-packaging grocery stores, improving the social and environmental impacts of the food supply chain [ 78 ]. Another example of the importance of consumer behavior is the ban on SUPBs in Chile [ 63 ], which was driven by a broad concern among the general public, and led to a bottom-up movement culminating in the national government taking stakes in the issue.

Literature also analyzed the consumer perceptions of microplastics in “personal care products” [ 83 ], of using “compostable carrier bags” [ 84 ], and “plastic water bottles” [ 81 ]. Orset et al. [ 81 ] analyzed the perception and behavior of consumers of plastic water bottles, which depend on the viewpoint (i.e., consumer, producer, and social welfare). From the consumer point of view, the authors recommended the organic policy with subsidy, the three tools of the recycling policy, and the biodegradable policy with subsidy. Concerning the compostable carrier bags [ 84 ], a greater awareness was observed regarding the use of these bags and the recognition of the importance of green products, which are gaining space in the market and in the routine of consumers. Furthermore, about microplastics in personal care products [ 83 ], participants of the survey perceived the use of microbeads in such products as unnatural and unnecessary.

Engineering

From the Scopus search about consumer awareness of plastic limited to the engineering area, a total of 131 authors’ keywords were obtained in the 33 publications (24 articles and 9 reviews). The most frequently used keywords by the authors of the engineering area are as follow (frequency of occurrence in parenthesis): mechanical properties (3), bio-based plastic (2), composites (2), consumer preferences (2), and food waste (2). All the other keywords present the same frequency.

The word cloud containing the 50 more frequently found authors’ keywords in the results of the Scopus search of the engineering area is shown in Fig.  5 .

figure 5

Word cloud containing the 50 principal authors’ keywords of the engineering area

Based on the analysis of the authors’ keywords, the engineering area demonstrates some options to mitigate the impacts that plastic pollution can cause; options such as the “circular economy,” “e-waste management,” the use of “biodegradable polymers” [ 85 ], “bio-based plastic” [ 73 ], “composites” [ 86 ], “chitosan” [ 87 ], “eco-friendly plastic,” “bioplastic,” “bamboo” [ 88 ], “alginate” [ 87 ], “biobased” and “biodegradable” [ 89 , 90 , 91 ], “bio nanocomposites” [ 92 ], “CO 2 -derived products” [ 93 ], and “filler” materials. All these materials are possible options for producing materials that are more environmentally friendly.

As an example of using biobased/biodegradable polymer, some authors [ 91 ] studied the feasibility of biobased/biodegradable films for in-package thermal pasteurization made of polylactic acid (PLA) and polybutylene adipate terephthalate (PBAT). The results indicated that selected PLA and PBAT-based films are suitable for in-package pasteurization and can replace polyethylene for ≤ 10 days of shelf life at 4 °C.

This area focuses on economic aspects to encourage the use of materials that cause less environmental impacts, such as “demonetization”  and a “cashless economy”  since financial encouragement is considered an effective way to reduce plastic debris [ 76 ]. “Credible alternative actions and products offered by businesses or through legislation at competitive costs can produce positive behavior changes that eventually reduce plastic pollution” [ 17 ].

The area also alerts people to a material that causes a substantial environmental impact, the ‘Brazil coffee-in-capsules’ [ 94 ]. According to the authors [ 94 ], coffee consumers have a dominant role in helping turn coffee capsule waste into a financial resource or supporting other efforts toward circular practice, emphasizing the behavior and awareness of consumers.

This attitude also raises an alert of possible problems to human health caused/aggravated by the use of plastics with the presence of the keywords “endocrine disruption,” “carcinogenesis,” “allergen,” and “biogenic toys” [ 74 ] (to avoid “children contamination” [ 95 ]). These keywords express some consumer concerns about the use of plastics.

Even knowing that packages act as a kind of barrier protecting food against damage, extending the lifetime of foods [ 5 , 33 ], and reducing food waste [ 78 , 96 ] (another keyword present in the word cloud), additives contained in plastic can migrate from packaging to the food due to diffusion processes (keyword “food contact material,” also shown in the word cloud). As an example of the diffusion process, the release of bisphenol A (BPA), a monomer used in the manufacture of epoxy resins, from polycarbonate products such as plastic baby bottles, baby bottle liners, and reusable drinking bottles is proven by literature [ 97 , 98 , 99 ]. BPA (endocrine-disrupting chemical) is toxic and can cause several health problems, from cancer to the development of problems in the formation of sexual organs of babies and children, depending on the contamination level [ 98 ]. Additionally, additives can contaminate soil, air, water, and food [ 100 , 101 ].

The research area also demonstrates the critical role of consumers regarding plastic use and its environmental impact through the keywords “consumer preferences” and “awareness” [ 78 , 102 ].

Materials Science

From the Scopus search about consumer awareness of plastic limited to materials science, 72 authors’ keywords were obtained in the 28 publications (20 articles and 8 reviews). The most frequently used keywords by the authors of the materials science area are as follow (frequency of occurrence in parenthesis): recycling (3), antibacterial (2), and mechanical properties (2). All the other keywords presented the same frequency. The smallest frequency of the keywords of the engineering and materials science compared to the environmental science area is due to the smaller number of publications and authors’ keywords.

The word cloud containing the 50 more frequently found authors’ keywords in the results of the Scopus search of the materials science area is shown in Fig.  6 .

figure 6

Word cloud containing the 50 main authors’ keywords of the materials science area

The keywords of the materials science area seem to show more significant concerns about the materials that compose the plastic, such as “high-density polyethylene” (HDPE) [ 103 ], “aliphatic polyesters” [ 90 ], “PET” (polyethylene terephthalate) [ 104 , 105 ], “additives” [ 106 ], “antioxidants,” “kenaf fiber” [ 107 ], “antifogs” [ 106 ], “bamboo” [ 88 ], “dyes/pigments” [ 108 ], “bamboo rayon” [ 109 ], “copper nanoparticles,” and “biodegradable polymers” [ 89 , 90 ]. Some of these keywords express the search for more environmentally friendly materials (for instance, the use of “natural fibers” [ 110 ] and “biodegradable polymers” [ 89 , 90 ]), aiming at reducing environmental impacts caused by plastic.

Concerning materials, a meaningful example is the one by Stoll et al. [ 108 ], which analyzed the use of carotenoid extracts as natural colorants in PLA films. According to the authors, using carotenoids as colorants for polymeric materials represents an environmentally friendly way of obtaining colored packaging. Beyond the environmental advantages, this natural colorant reduced the oxygen permeability and presented a lubricant effect, increasing the film elasticity up to 50%. Some authors [ 110 ] investigated the processing of natural fibers in an internal mixer to be used for thermoplastic lightweight materials, which means a good alternative for the automotive industry.

The primary possibility to solve the problem of plastic waste posed by the area is “recycling” and others, such as the use of plastic residues in the production of “lightweight concrete” [ 111 ], “construction materials,” “composites,” and in “3D printing” [ 104 ]. 3D printing is an option for the recycling process of post-used plastics, as in the example of using PET [ 104 ].

Biodegradable polymers can be considered an option to reduce solid waste disposal problems and reduce the dependence on petroleum-based plastics for packaging materials [ 90 ]. However, some authors [ 89 ] detected some problems, namely, cost control, in-depth development of functions and applications, materials source extension, enhancement of environmental protection awareness and regulations, and systematical assessment of environmental compatibility of the biodegradable polymers.

All these possibilities should present the necessary mechanical properties for their specific final applications, demonstrated by the keywords “mechanical properties,” “compliance,” and “durability.” Also, the keywords “finite element analysis,” “kinetics,” “computational fluid dynamics” [ 112 ], and “package design” indicate some possibilities for analyzing the properties of a given material and design. Computational fluid dynamics (the “finite volume method”) was used to analyze the airflow and the heat transfer performances in the design and performance evaluation of fresh fruit ventilated distribution packaging by Mukama et al. [ 112 ], being that the vent-hole design affects cooling and strength requirements.

Some health impacts of plastic and some benefits are also presented, such as “heavy metal testing” [ 105 ], “antimicrobial” [ 113 , 114 ], “antibacterial” [ 109 ], “exposure” [ 115 ], and “antimicrobial fruit quality.” The research area does not demonstrate the role of consumers in the problems that plastic can cause. However, it presents some possibilities for consumers to act actively and consciously through the presence of keywords “chemical education research” [ 116 ], “evaluation strategies,” and “environmental protection.”

Concerning the use of recycled polymers, some authors [ 117 ] analyzed the removal of the odor from HDPE by using a modified recycling process. Removing this type of contamination is considered a challenge in the industry and vital to establishing viable concepts for a circular economy for post-consumer HDPE packaging.

Based on the analysis of the authors’ keywords, the materials science area is more focused on solving environmental problems caused by plastic through designing and producing materials that cause a lower environmental impact and are more environmentally friendly options. It is also a way to make consumers more aware of their role when using plastics, providing consumers with options that cause less environmental impact.

The work of Rhein and Schmid [ 68 ], which verified the real concerns of consumers regarding plastic packaging from a quantitative analysis based on consumers interviews, showed that consumer awareness involves the following five different aspects:

Awareness of environmental pollution: consumer awareness of the damage that plastic pollution causes to the environment and the oceans, knowing the necessity of environmental protection.

Awareness of the intensive use of plastic: consumers who are aware of the problems that plastic can cause but, even so, still use it unreasonably.

Awareness of consumers’ influence: even being aware, these consumers are concerned about companies and the influence caused by them.

Awareness of consumers’ powerlessness: consumers do not know how to contribute to the reduction of plastic pollution.

Awareness of the need for using plastic: consumer awareness of the positive characteristics of plastic making it essential in their daily lives, such as a hygienic way of storage.

According to the authors [ 68 ], “the different types of awareness strongly reflect how consumers think about problems associated with plastic and whether they feel that they are responsible and, therefore, able to change the current situation.”

As stated before, consumers may not want to put information into practice on individual actions relative to environmental and economic benefits [ 17 ]. In other words, many consumers have the information they need to dispose of plastic waste correctly and would rather avoid cooperating. So, consumers have a crucial role in the correct segregation and final disposal of plastic waste, but, unfortunately, some do not fulfill their role (Fig.  1 ), and consequently, several socio-environmental problems caused by plastic are aggravated. An example that can be observed daily is the significant increase in the number of face masks improperly disposed of on the streets during the COVID-19 pandemic. They end up going into water bodies and can kill animals (Fig.  1 ). These masks are degraded and release plastic microparticles [ 23 , 33 , 118 ].

Behavior changes can be blocked by psychological and practical barriers, turning the awareness raising into tortuous action [ 119 ]. Plastic-related behavioral change is not very successful if the focus is only on information and raising awareness [ 65 ]. Stakeholders interviewed by Steinhorst and Beyerl [ 120 ] agreed that consumers are not the most responsible agents of change but rather partners of producers, retailers, politicians, and disposal agencies, in which producers and retailers are considered the main agents. Private and public sector initiatives, well-enforced policies, and evidence-based media reporting can provide new norms and practices that are socially accepted [ 17 ]. According to Parashar and Hait [ 69 ], the primary drivers of plastic misconduct are the lack of awareness and attitude of consumers and their irresponsible behavior, as well as the stress on waste management infrastructure in terms of collection, operation, and financial constraints.

The impact of COVID-19 on people’s consumption behavior worldwide was studied [ 121 ], having the following as main results:

Increased the consumption of packed food and food delivery (i.e., increased the number of packages consumed) during the pandemic (45–48% of the respondents)

Increased waste generation during the lockdown period, being the highest increase observed for plastic packaging (53%) and food waste (45%) (55% of the respondents)

Efforts increasing to segregate waste properly during the lockdown (32% of the respondents)

The need to use less packaging through new product design (66% of the respondents) or to increase recyclability (61% of the respondents)

These results reveal the increase in the production of recyclable materials in homes and the lack of environmental awareness of most of the respondents. Contradictorily, just 32% segregated the waste they produced but demonstrated concern about the new design of packaging containing less plastic.

Likewise, Rhein and Schmid [ 68 ] demonstrated a similar profile of consumers and their awareness of the use of plastic. At the same time, some consumers are willing to pay more for other options that cause less pollution, citing concern for families and especially grandchildren. They claim that plastic pollution is the fault of Africa, Asia, and the Americas (i.e., outside Europe, where the research was performed). They know that the amount of plastic used in packages is large and sometimes unnecessary, such as plastic in shell fruits. However, these consumers cannot help change and assign responsibility to companies. A particular sort of laziness and a wish to buy goods without restrictions override the consciousness that the existing plastic system would, in principle, be changed. Some consumers are conscious of the use of plastic and know the problems they cause to the environment but agree that plastic is practical, unwilling to alter their consumption behavior. That is, “others” are responsible for pollution, not “me.”

Considering consumers’ daily consumption, hygiene, food safety, and practicality of use are more important than the environmental impact [ 122 ]. In the review of Heidbreder et al. [ 65 ], in which 187 studies were analyzed, people appreciate and regularly use plastic despite a noticeable awareness of related problems. Also, Nguyen [ 123 ] analyzed factors that affect Vietnamese consumers’ intention and behavior to bring their shopping bags (BYOB). The results illustrated a modest relationship between intent and authentic behavior concerning BYOB.

So, the literature shows a gap between consumer awareness and behavior. The literature needs to be focused on reducing this gap. According to Ali et al. [ 22 ], there is a lack of literature about the explicit roles of consumers, corroborating with the present work. The interrelationships among the consumer’s roles were identified by the authors, which provided action plans for decreasing plastic pollution.

According to the obtained results, each knowledge area has its concerns and priorities regarding consumer awareness of plastic. Nevertheless, such concerns and priorities are not in line with the ones of consumers in everyday life. Thus, by reducing this gap, literature can be a strong partner, for example, in the decision-making of authorities, such as in the creation of laws and norms aimed at reducing the real problem of the final disposal of plastic waste. “Consumers-citizens can greatly contribute to solving the plastic pollution problem and can be used as a stepping stone for further interdisciplinary research” [ 17 ].

As an example of the magnitude of the literature, Wang et al. [ 124 ] systematically reviewed and compared the publications related to plastic pollution before and during the COVID-19 pandemic. Among the main results, the authors observed that the total number of publications during the COVID-19 pandemic has been much higher than before, and this increase happened in a short period, demonstrating increasing attention to research on plastic pollution worldwide promoted by the COVID-19 pandemic. Another relevant case is Contact From the Future , a digital game on plastic pollution for children created by Panagiotopoulou et al. [ 125 ], which proposed to construct awareness and motivate pro-environmental behaviors.

As stated before by some authors [ 68 ], in the literature, consumer awareness of plastic is, in general, intrinsically linked to the consumers’ environmental awareness. The results from this work show that consumer awareness of plastic is broader, not limited to environmental consciousness, and each knowledge area has its concerns. These results align with Rhein and Schmid [ 68 ], which depicted that “the term awareness cannot automatically be equated with environmental concerns”.

Based on the analysis of the authors’ keywords, the environmental area is prone to concerns; engineering is focused on the solutions, and materials science in the materials that compose the plastic and the development of alternative materials. All of them are intrinsically connected in an attempt to mitigate the pollution caused by plastic. In other words, consumer awareness of plastic is a much broader issue, not just an environmental concern. Even knowing the importance of all the areas analyzed in the search for the growth of consumer awareness of plastic, it is perceived that the literature is not aligned with consumer awareness in their daily life. Literature needs, in addition to focusing on addressing deficiencies described above, meet the real requests of the population in the search for awareness and behavior change for the well-being of society. A schema is shown in Fig.  7 .

figure 7

Schema shows that even if the various areas of knowledge about consumer awareness of plastic have several concerns, these do not seem to align with the population’s concerns

So, after all, how to raise consumer awareness of plastic? The literature has provided an outstanding contribution to this.

Integrated plastic waste management is a very complex issue and requires engagement at all levels, including producer, consumer, and government. The government is mainly responsible for establishing laws aimed at the common good and supervision so that they are fulfilled. As an example of Law Nº 12,305 in Brazil [ 126 ], laws addressing waste management highlight the shared responsibility in which consumers have an essential role.

Public policies are relevant, mainly in cases of consumers who, even knowing their role in the circular economy, do nothing for laziness, selfishness, or lack of awareness. They must change consumer habits through impositions when they do not collaborate. Some consumers contribute from a stimulus, a “currency of exchange,” collaborating only from some advantage. In this sense, it is up to the industries responsible for the reverse logistics of their products to encourage consumers in some way that seems feasible for them to contribute to reverse logistics and the circular economy.

Some authors [ 127 ] compared the result of focus group sessions in India with literature about sustainable packages for Fast Moving Consumer Goods (FMCG). Higher environmental awareness was observed in groups with higher levels of schooling. Young generations, especially those still attending school, have shown more awareness and concern about making sustainable choices, while older generations have shown a significant lack of awareness. Conversely, price is one of the most significant factors deterring purchase. Also, a lack of knowledge about the benefits offered by sustainable products makes consumers indifferent toward them.

Similar behavior was observed by Molloy et al. [ 128 ], which examined the perception of legislative actions on single-use plastics through surveys and interviews in four Atlantic provinces of Canada. Young generations, students, and high-level school people support the plastic ban. A higher percentage of females support the plastic ban. Men have less probability of contributing to environmentally friendly activities, such as carrying reusable bags.

In Islamabad Capital Territory of Pakistan [ 129 ], people who support the plastic bag ban are those with a high education level, health, and environmental awareness. According to the authors, to increase the effectiveness of Islamabad’s plastic bag ban, increasing public understanding of the effects of plastic pollution needs to receive more focus by investing money in awareness programs and campaigns, education investment, and proper implementation machinery.

In Ecuador [ 130 ], reusable bags are more likely to be used by the head of household with a high-education level and the rural population. On the other hand, the probability of using these bags reduces when the head of household participates in social organizations.

In Turkey, the use of free-of-charge plastic bags was banned. After this, some authors observed that, among the Istanbul population, women, married people, and high-income groups are more prone to consume plastic bags [ 131 ]. These groups should be considered the focal point when designing policies. Based on the authors, “policymakers and environmental organizations should provide the necessary campaigns and training to reignite the tendency to reduce plastic bag consumption as part of environmental awareness.”

There are also cases where the consumer does not contribute to the circular economy due to a lack of knowledge. For example, the survey results found that university students are unaware of the consequences of beverage packaging material choices on environmental sustainability [ 132 ]. They do not know how to contribute effectively in their day-by-day activities to the sustainability goal.

More environmentally conscious people are more prone to join environmental initiatives [ 128 , 129 , 133 ]. “Information is one of the most widely used means to promote pro-environmental behavior change” [ 134 ] and, consequently, make consumers aware of plastic and its impacts. So, education is an effective way to raise consumer awareness of plastic.

The Internet can improve consumers’ pro-environmental behavior [ 135 ]. The Internet has the leading role in providing environmental information, making environmental knowledge popular, and enhancing energy use and social relationships [ 135 ]. Moreover, communication through mass media as TV channels open to the public is essential means of information about plastic pollution. Additionally, shocking images, messages of victims of plastic waste, and emotive images are effective in developing consumer awareness since they attract the consumers’ attention and produce a debate on plastic use [ 136 , 137 ]. “The media has a critical role in educating the public and policymakers on the current environmental concerns regarding plastic pollution” [ 22 ].

Last but not least, the plastic importance must be clear to everyone, no matter the way.

Conclusions

It is common in different areas of knowledge to have distinct interests. In an interdisciplinary area such as consumer awareness of plastic consumption and its paramount importance to society, it would be ideal for interests to converge for the well-being of society.

It was possible to observe that each area (environmental science, engineering, and materials science) presents different strategies to reduce the negative impact of plastic on human health and the environment. Each area contributes on its area in developing consumer awareness of plastic:

The environmental science area seems to be focused on consumer accountability for problems that plastic can cause.

Engineering seems to analyze the plastic problem in a more broadly way, depicting some causes, problems that plastic can cause, and possible solutions to solve them.

Materials science seems to be focused on the materials that compose the plastic, bringing some opportunities for materials that cause less impact on the environment, such as the ones from renewable sources.

Concerning the analysis of the authors’ keywords:

The main hotspots are waste management, recycling, sustainability, plastic waste, packaging, consumer behavior, microplastics, pollution, and biopolymers.

The main trends are biopolymers, recycling, sustainability, waste management, food safety, health impact, mechanical properties, microplastics, and packaging.

The main emerging topics are plastic waste, sustainability, waste management, recycling, microplastics, and pollution.

The primary deficiencies or gaps in the literature are in the following categories: actors, mitigations, and policies.

So, the authors’ keywords analysis can describe the current scenario of consumer awareness of plastic literature and depict the main concerns of the authors. The analysis can also help outline the future of the research area based on filling in identified deficiencies.

However, all these concerns are not aligned with the ones of the consumer’s habit. It is a severe gap in which literature needs to turn, reducing the “distance” between consumer awareness and behavior.

Data Availability

Not applicable.

Code Availability

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de Sousa, F.D.B. Consumer Awareness of Plastic: an Overview of Different Research Areas. Circ.Econ.Sust. 3 , 2083–2107 (2023). https://doi.org/10.1007/s43615-023-00263-4

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  • Synthesizing Sources | Examples & Synthesis Matrix

Synthesizing Sources | Examples & Synthesis Matrix

Published on July 4, 2022 by Eoghan Ryan . Revised on May 31, 2023.

Synthesizing sources involves combining the work of other scholars to provide new insights. It’s a way of integrating sources that helps situate your work in relation to existing research.

Synthesizing sources involves more than just summarizing . You must emphasize how each source contributes to current debates, highlighting points of (dis)agreement and putting the sources in conversation with each other.

You might synthesize sources in your literature review to give an overview of the field or throughout your research paper when you want to position your work in relation to existing research.

Table of contents

Example of synthesizing sources, how to synthesize sources, synthesis matrix, other interesting articles, frequently asked questions about synthesizing sources.

Let’s take a look at an example where sources are not properly synthesized, and then see what can be done to improve it.

This paragraph provides no context for the information and does not explain the relationships between the sources described. It also doesn’t analyze the sources or consider gaps in existing research.

Research on the barriers to second language acquisition has primarily focused on age-related difficulties. Building on Lenneberg’s (1967) theory of a critical period of language acquisition, Johnson and Newport (1988) tested Lenneberg’s idea in the context of second language acquisition. Their research seemed to confirm that young learners acquire a second language more easily than older learners. Recent research has considered other potential barriers to language acquisition. Schepens, van Hout, and van der Slik (2022) have revealed that the difficulties of learning a second language at an older age are compounded by dissimilarity between a learner’s first language and the language they aim to acquire. Further research needs to be carried out to determine whether the difficulty faced by adult monoglot speakers is also faced by adults who acquired a second language during the “critical period.”

Prevent plagiarism. Run a free check.

To synthesize sources, group them around a specific theme or point of contention.

As you read sources, ask:

  • What questions or ideas recur? Do the sources focus on the same points, or do they look at the issue from different angles?
  • How does each source relate to others? Does it confirm or challenge the findings of past research?
  • Where do the sources agree or disagree?

Once you have a clear idea of how each source positions itself, put them in conversation with each other. Analyze and interpret their points of agreement and disagreement. This displays the relationships among sources and creates a sense of coherence.

Consider both implicit and explicit (dis)agreements. Whether one source specifically refutes another or just happens to come to different conclusions without specifically engaging with it, you can mention it in your synthesis either way.

Synthesize your sources using:

  • Topic sentences to introduce the relationship between the sources
  • Signal phrases to attribute ideas to their authors
  • Transition words and phrases to link together different ideas

To more easily determine the similarities and dissimilarities among your sources, you can create a visual representation of their main ideas with a synthesis matrix . This is a tool that you can use when researching and writing your paper, not a part of the final text.

In a synthesis matrix, each column represents one source, and each row represents a common theme or idea among the sources. In the relevant rows, fill in a short summary of how the source treats each theme or topic.

This helps you to clearly see the commonalities or points of divergence among your sources. You can then synthesize these sources in your work by explaining their relationship.

If you want to know more about ChatGPT, AI tools , citation , and plagiarism , make sure to check out some of our other articles with explanations and examples.

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various sources of research literature

Synthesizing sources means comparing and contrasting the work of other scholars to provide new insights.

It involves analyzing and interpreting the points of agreement and disagreement among sources.

You might synthesize sources in your literature review to give an overview of the field of research or throughout your paper when you want to contribute something new to existing research.

A literature review is a survey of scholarly sources (such as books, journal articles, and theses) related to a specific topic or research question .

It is often written as part of a thesis, dissertation , or research paper , in order to situate your work in relation to existing knowledge.

Topic sentences help keep your writing focused and guide the reader through your argument.

In an essay or paper , each paragraph should focus on a single idea. By stating the main idea in the topic sentence, you clarify what the paragraph is about for both yourself and your reader.

At college level, you must properly cite your sources in all essays , research papers , and other academic texts (except exams and in-class exercises).

Add a citation whenever you quote , paraphrase , or summarize information or ideas from a source. You should also give full source details in a bibliography or reference list at the end of your text.

The exact format of your citations depends on which citation style you are instructed to use. The most common styles are APA , MLA , and Chicago .

Cite this Scribbr article

If you want to cite this source, you can copy and paste the citation or click the “Cite this Scribbr article” button to automatically add the citation to our free Citation Generator.

Ryan, E. (2023, May 31). Synthesizing Sources | Examples & Synthesis Matrix. Scribbr. Retrieved March 9, 2024, from https://www.scribbr.com/working-with-sources/synthesizing-sources/

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6 in 10 US adults doubt mental capability of Biden and Trump, AP-NORC poll finds

63% of U.S. adults say they lack confidence in Biden’s mental capability to serve effectively as president, according to a new survey by The Associated Press-NORC Center for Public Affairs Research.

FILE - President Joe Biden delivers his State of the Union speech to a joint session of Congress, at the Capitol in Washington, Feb. 7, 2023. A poll shows that a growing share of U.S. adults doubt that 81-year-old President Joe Biden has the memory and acuity for the job. That means Biden's upcoming State of the Union address could be something of a real-time audition as he bids for a second term. (AP Photo/J. Scott Applewhite, File)

FILE - President Joe Biden delivers his State of the Union speech to a joint session of Congress, at the Capitol in Washington, Feb. 7, 2023. A poll shows that a growing share of U.S. adults doubt that 81-year-old President Joe Biden has the memory and acuity for the job. That means Biden’s upcoming State of the Union address could be something of a real-time audition as he bids for a second term. (AP Photo/J. Scott Applewhite, File)

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WASHINGTON (AP) — A poll finds that a significant share of U.S. adults doubt the mental capabilities of 81-year-old President Joe Biden and 77-year-old Donald Trump, the former president and current Republican front-runner in what could be a rematch of the 2020 election.

More than 6 in 10 (63%) say they’re not very or not at all confident in Biden’s mental capability to serve effectively as president, turning his coming State of the Union address into something of a real-time audition for a second term. A similar but slightly smaller share (57%) say that Trump lacks the memory and acuity for the job.

The findings from a new survey by The Associated Press-NORC Center for Public Affairs Research point to a tough presidential election in which issues such as age and mental competence could be more prevalent than in any other political contest in modern times.

People’s views of Biden’s memory and acuity have soured since January 2022, when about half of those polled expressed similar concerns. (That survey didn’t ask a similar question about Trump.)

FILE - President Joe Biden and first lady Jill Biden stand on stage after Biden spoke in Blue Bell, Pa., Jan. 5, 2024. First lady Jill Biden says her husband’s age is an “asset,” as President Joe Biden faces persistent questions from voters about his decision to seek another term at age 81. Joe Biden already is the oldest American leader in history. (AP Photo/Matt Rourke, File)

In a major risk for Biden, independents are much more likely to say that they lack confidence in his mental abilities (80%) compared with Trump’s (56%). And Democrats are generally more concerned about Biden’s mental capabilities than Republicans are with Trump’s, raising the stakes of Biden’s upcoming speech to a joint session of Congress on Thursday.

AP AUDIO: 6 in 10 US adults doubt mental capability of Biden and Trump, AP-NORC poll finds.

AP correspondent Josh Boak reports a new poll finds a majority of Americans are concerned about both President Biden and Donald Trump’s capability on the job.

Going into the big event, just 38% of U.S. adults approve of how Biden is handling his job as president, while 61% disapprove. Democrats (74%) are much likelier than independents (20%) and Republicans (6%) to favor his performance. But there’s broad discontent on the way Biden is handling a variety of issues, including the economy, immigration and foreign policy.

About 4 in 10 Americans approve of the way Biden is handling each of these issues: health care, climate change, abortion policy and the conflict between Russia and Ukraine. But people are less satisfied by Biden’s handling of immigration (29%), the conflict between the Israelis and the Palestinians (31%) and the economy (34%) — all of which are likely to come up in the speech before a joint session of Congress.

Nearly 6 in 10 (57%) Americans think the national economy is somewhat or much worse off than before Biden took office in 2021. Only 3 in 10 adults say it’s better under his leadership. Still, people are more optimistic about the state of their own bank accounts: 54% say their personal finances are good.

Many respondents to the survey were deeply pessimistic about their likely choices in November because of age and the risk of cognitive decline.

Paul Miller, himself 84, said Biden is just too old — and so is Trump.

“He doesn’t seem to have the mental whatever to be a president,” Miller said of Biden. He added that Trump is “too old, too, and half crazy.”

President Joe Biden delivers the State of the Union address to a joint session of Congress at the Capitol, Thursday, March 7, 2024, in Washington. Standing at left is Vice President Kamala Harris and seated at right is House Speaker Mike Johnson, R-La. (Shawn Thew/Pool via AP)

The retiree from Carlisle, Pennsylvania, said he voted for Trump in 2020 but he wouldn’t do so again.

“I don’t think I’m going to vote for either one of them,” he said. “I hope somebody else is available.”

The president faces added pressure about his age after unflattering descriptions of him contained in a special counsel’s report that did not recommend criminal prosecution of Biden for his mishandling of classified records, unlike Trump who was indicted for keeping classified material in his Florida home. The report said that Biden’s memory was “hazy,” “fuzzy,” “faulty,” “poor” and had “significant limitations.”

Biden has tried to deflect concerns by joking about his age and taking jabs at Trump’s own gaffes. Yet the president’s age is a liability that has overshadowed his policy achievements on infrastructure, manufacturing and addressing climate change.

About one-third of Democrats said they’re not very or not at all confident in Biden’s mental capability in the new survey, up from 14% in January 2022. Only 40% of Democrats said they’re extremely or very confident in Biden’s mental abilities, with approximately 3 in 10 saying they’re “somewhat” confident.

Republicans are generally more comfortable with Trump’s mental capabilities than Democrats are with Biden’s. In the survey, 59% of Republicans are extremely or very confident that Trump has the mental abilities to be president. An additional 20% are somewhat confident, and 20% are not very or not at all confident.

But if there is one thing Democrats and Republicans can agree upon, it’s that the other party’s likely nominee is not mentally up to the task. About 9 in 10 Republicans say Biden lacks the mental capability to serve as president, while a similar share of Democrats say that about Trump.

Part of Biden’s problem is that his policies have yet to break through the daily clutter of life.

Sharon Gallagher, 66, worries about inflation. She voted for Biden in 2020, but believes he has not done enough for the economy. She also feels Trump is a bit too quick to anger. The Sarasota, Florida, resident said she doesn’t have the bandwidth to really judge their policies.

“I don’t pay enough attention to politics to even know,” Gallagher said. “I have grandchildren living with me and I have children’s shows on all day.”

Justin Tjernlund, 40, from Grand Rapids, Michigan, said Biden “seems like he’s mostly still there,” but even if he was in decline he has “a whole army of people to help him do the job.” Trjenlund said he voted for Trump in 2020 and plans to do so again because the Republican is “interesting” and “refreshing.”

Still, because of both candidates’ ages, Greg Olivo, 62, said he plans to focus on Vice President Kamala Harris and whomever Trump, if he’s the nominee, picks for a running mate.

“Keep a close eye on the vice president,” said the machinist from Valley City, Ohio, who voted for Biden in 2020 and would do so again. “Because that person will probably be the president in four years, one way or another.”

The poll of 1,102 adults was conducted Feb. 22-26, 2024, using a sample drawn from NORC’s probability-based AmeriSpeak Panel, which is designed to be representative of the U.S. population. The margin of sampling error for all respondents is plus or minus 4.1 percentage points.

Associated Press polling reporter Linley Sanders contributed.

JOSH BOAK

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COMMENTS

  1. Types of Sources Explained

    Books Websites Newspapers Encyclopedias The type of source you look for will depend on the stage you are at in the writing process. For preliminary research like definitions and broad overviews, you might consult an encyclopedia or a website.

  2. Literature review sources

    Books. Textbooks remain as the most important source to find models and theories related to the research area. Research the most respected authorities in your selected research area and find the latest editions of books authored by them.

  3. Researching for your literature review: Literature sources

    A good quality literature review involves searching a number of databases individually. The most common method is to search a combination of large inter-disciplinary databases such as Scopus & Web of Science Core Collection, and some subject-specific databases (such as PsycInfo or EconLit etc.). The Library databases are an excellent place to ...

  4. How to Find Sources

    There are three main places to look for sources to use in your research: Research databases Your institution's library Other online resources Table of contents Research databases Library resources Other online sources Other interesting articles Frequently asked questions about finding sources Research databases

  5. Types of Literature

    Conference paper Scholarly (aka empirical) article -- example Empirical studies use data derived from observation or experiment. Original research papers (also called primary research articles) that describe empirical studies and their results are published in academic journals.

  6. Literature search for research planning and identification of research

    INTRODUCTION. Literature search is a systematic and well-organised search from the already published data to identify a breadth of good quality references on a specific topic.[] The reasons for conducting literature search are numerous that include drawing information for making evidence-based guidelines, a step in the research method and as part of academic assessment.[]

  7. How to Write a Literature Review

    Step 1 - Search for relevant literature Step 2 - Evaluate and select sources Step 3 - Identify themes, debates, and gaps Step 4 - Outline your literature review's structure Step 5 - Write your literature review Free lecture slides Other interesting articles Frequently asked questions Introduction Quick Run-through Step 1 & 2 Step 3 Step 4 Step 5

  8. 5. The Literature Review

    Definition A literature review surveys prior research published in books, scholarly articles, and any other sources relevant to a particular issue, area of research, or theory, and by so doing, provides a description, summary, and critical evaluation of these works in relation to the research problem being investigated.

  9. Guidance on Conducting a Systematic Literature Review

    For instance, Pawson suggests completing different sections of an extraction form for different sources or simply highlighting relevant sentences (Pawson et al. 2005, 30). ... After an initial search of literature on the research question, the researchers can conduct a quick mapping procedure to identify the kinds of research activities related ...

  10. Reviewing the research methods literature: principles and strategies

    The conventional focus of rigorous literature reviews (i.e., review types for which systematic methods have been codified, including the various approaches to quantitative systematic reviews [2-4], and the numerous forms of qualitative and mixed methods literature synthesis [5-10]) is to synthesize empirical research findings from multiple ...

  11. Literature of Science

    summarizes the differences between different types of journals and popular magazines. ... Journal papers are the basic "molecular" unit of scientific knowledge base and are the most important "primary" source in the sciences. More than 80% of the scientific research literature is published in this format. Annually 1.5 million articles are ...

  12. Methodological Approaches to Literature Review

    A literature review is defined as "a critical analysis of a segment of a published body of knowledge through summary, classification, and comparison of prior research studies, reviews of literature, and theoretical articles." (The Writing Center University of Winconsin-Madison 2022) A literature review is an integrated analysis, not just a summary of scholarly work on a specific topic.

  13. Literature Review: Lit Review Sources

    Lit Review Types GRADE System Do a Lit Review Citation Justice Lit Review Sources Readings Where do I find information for a literature review? Research is done by... Click image to enlarge ...by way of... Critical Evaluations Interpretive Work Research (empirical) "Grey" literature (identify trends) College reports Curriculum documents Handouts

  14. Primary & Secondary Sources

    The Literature The Literature refers to the collection of scholarly writings on a topic. This includes peer-reviewed articles, books, dissertations and conference papers. When reviewing the literature, be sure to include major works as well as studies that respond to major works.

  15. (PDF) LITERATURE REVIEW, SOURCES AND METHODOLOGIES

    What are the possible sources of literature I can use? Discover the world's research Content uploaded by Philippa Ojimelukwe Author content Content may be subject to copyright. SciELO....

  16. Primary and secondary sources

    Source documents include theses, unpublished articles, government reports, conference papers, abstracts, book chapters, books, discussion and working papers, and statistical documents. National Archive of Australia - The National Archives of Australia holds the memory of our nation and keeps vital Australian Government records safe.

  17. Literature review as a research methodology: An ...

    This paper discusses literature review as a methodology for conducting research and offers an overview of different types of reviews, as well as some guidelines to how to both conduct and evaluate a literature review paper. It also discusses common pitfalls and how to get literature reviews published. 1.

  18. Chapter 4: Where to Find the Literature

    You will go back into the literature throughout the writing of your literature review as you uncover gaps in the evidence and as additional questions arise. Figure 4.1 4.2 Finding sources: Places to look. Let's take some time to look at where the information sources you need for your literature review are located, indexed, and stored.

  19. 5.3 Acceptable sources for literature reviews

    5.3 Acceptable sources for literature reviews ... The following sections will explain and provide examples of these various sources. Peer reviewed journal articles (papers) ... What this means is that two to three experts in the area of research featured in the paper have reviewed and accepted the paper for publication. The names of the author ...

  20. Types of Literature

    Research literature is an essential component of your literature review. Theory-based Literature Literature that is informed and tested by research, these books, articles and reference sources will attempt to explain, describe, define and provide a background or theoretical framework for a field of inquiry.

  21. Scholarly Literature Types

    The sources you select will be informed by your research question and field of study, but should likely include, at a minimum, theses and dissertations. Why Search the Gray Literature? Most of gray literature is considered less prestigious, reliable, and "official" than publication in a peer-reviewed journal.

  22. How To Write Synthesis In Research: Example Steps

    On This Page: Step 1 Organize your sources. Step 2 Outline your structure. Step 3 Write paragraphs with topic sentences. Step 4 Revise, edit and proofread. When you write a literature review or essay, you have to go beyond just summarizing the articles you've read - you need to synthesize the literature to show how it all fits together (and ...

  23. A review of the global climate change impacts, adaptation, and

    To better understand the problem, gathered the information in this report from various media outlets, research agencies, policy papers, newspapers, and other sources. This review is a sectorial assessment of climate change mitigation and adaptation approaches worldwide in the aforementioned sectors and the associated economic costs.

  24. Consumer Awareness of Plastic: an Overview of Different Research Areas

    In this work, consumer awareness of plastic is discussed according to the point of view of the research areas—environmental science, engineering, and materials science—based on the analysis of the main authors' keywords obtained in a literature search in the Scopus database. Bibliometrix analyzed the Scopus search results.

  25. Synthesizing Sources

    A literature review is a survey of scholarly sources (such as books, journal articles, and theses) related to a specific topic or research question. It is often written as part of a thesis, dissertation , or research paper , in order to situate your work in relation to existing knowledge.

  26. Quanta Magazine

    Quanta Magazine

  27. JS 2230W

    Tags: jewish literature, jews, literature, south, southern VU Libraries ResearchGuides is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License . You may republish or adapt this guide for educational purposes, as long as proper credit is given.

  28. Fact checking Biden's State of the Union

    Britt on Biden suspending deportations Britt said that just after taking office in 2021, Biden "suspended all deportations." "President Biden inherited the most secure border of all time.

  29. Ahead of Biden's SOTU, more than 6 in 10 US adults doubt his mental

    Founded in 1846, AP today remains the most trusted source of fast, accurate, unbiased news in all formats and the essential provider of the technology and services vital to the news business. ... The findings from a new survey by The Associated Press-NORC Center for Public Affairs Research point to a tough presidential election in which issues ...