what is the scope of literature review

• Research guides

Writing a Literature Review

Phase 1: scope of review, it's a literature review of what, precisely.

Need to Have a Precise Topic It is essential that one defines a research topic very carefully. For example, it should not be too far-reaching. The following is much too broad:

"Life and Times of Sigmund Freud"

However, this is more focused and specific and, accordingly, a more appropriate topic:

"An Analysis of the Relationship of Freud and Jung in the International Psychoanalytic Association, 1910-1914"

Limitations of Study In specifying precisely one's research topic, one is also specifying appropriate limitations on the research. Limiting, for example, by time, personnel, gender, age, location, nationality, etc. results in a more focused and meaningful topic.  

Scope of the Literature Review It is also important to determine the precise scope of the literature review. For example,

• What exactly will you cover in your review?
• How comprehensive will it be?
• How long? About how many citations will you use?
• How detailed? Will it be a review of ALL relevant material or will the scope be limited to more recent material, e.g., the last five years.
• Are you focusing on methodological approaches; on theoretical issues; on qualitative or quantitative research?
• Will you broaden your search to seek literature in related disciplines?
• Will you confine your reviewed material to English language only or will you include research in other languages too?

In evaluating studies, timeliness is more significant for some subjects than others. Scientists generally need more recent material. However, currency is often less of a factor for scholars in arts/humanities. Research published in 1920 about Plato's philosophy might be more relevant than recent studies.

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Writing a literature review.

• Definitions

Determine the scope of your review

A review of what, planning your literature review.

• Finding sources
• Annotating sources
• Organizing the review
• Writing the review
• Practical Tips

The length of the review depends on your objective. 

• Are you writing a research paper as the final project in a specific course?
• Are you writing a senior or honor's capstone project or thesis? 
• Are you writing for an undergraduate or graduate course? 
• Are you writing a master's thesis? 
• Are you writing a dissertation?

The majority of these projects will require a selective examination of the literature.  Discuss the length of your review with your instructor or paper advisor.

• You must have a precise question to study. For example, your question cannot be too broad, nor too narrow. 
• You must understand the limitations of your research. Limiting by time, geographic area, gender, age, and/or nationality are all good ways to develop a more focused topic.
• what will you cover?
• will your coverage be selective or exhaustive?
• are you focusing on a specific theory or methodology; a specific type of research?
• will you include information published in other languages?
• will you include information from related disciplines?

It will take time to locate and review the literature relevant to your research question.  Starting early will allow you sufficient time to gather and review your sources.  The process of writing a literature review normally includes the following elements:

1. Defining your research question

2. Planning the approach to your review and research

3. Searching the literature

4. Analyzing the material you find

5. Organizing the review

6. Writing the review

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Literature review.

• Introduction to Literature Reviews
• Purpose and Scope
• Types of Lit Reviews
• Finding Published Literature Reviews
• Writing the Lit Review
• Books and Websites

The literature review analyzes relationships and connections among different works. This differs from an annotated bibliography which provides a list and brief description of articles, books, theses, and other documents. The literature review should not merely list and summarize one piece of research after another. 

Through analysis of major works and subsequent scholarship the lit review lays out the evolution of scholarship on a topic and establishes a context for further research. This will help you to establish why the topic is important and place your research in a theoretical context.

A literature review will help you to avoid redundancy in your own research and to identify new problems, possibilities for further research, and to expand upon or ask new questions. The literature review allows you as a researcher to enter into an ongoing conversation with other scholars and researchers.

A literature review may be comprehensive or selective but should examine seminal or principal works and works that have been consequential in the field. The scope of a literature review will vary by assignment and discipline. The literature review may be part of a larger work or a stand-alone article, meaning that it is the entirety of a paper. The literature review may be part of the introduction, or a separate section to a thesis, dissertation, or research report setting up the context for the author's original research.   The literature review:

• Compares and contrasts
• Identifies areas of consensus and dissent
• Reveals gaps or oversights
• Indicates areas needing further research
• Points out trends, themes, approaches, methodologies, theories, and frames of analysis
• Discusses major debates in the field
• Examines methodological or theoretical strengths and weaknesses

The importance of currency (timeliness of information) will vary by discipline and the purpose of the assignment. The sciences are typically more concerned with current research, practice, and findings. For example, in fields like health or medicine the lit review may only draw on recent literature which has been published within 5-10 years. However, inclusion of much older works is often relevant in fields such as the arts, humanities, philosophy, or history.

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How To Structure Your Literature Review

3 options to help structure your chapter.

By: Amy Rommelspacher (PhD) | Reviewer: Dr Eunice Rautenbach | November 2020 (Updated May 2023)

Writing the literature review chapter can seem pretty daunting when you’re piecing together your dissertation or thesis. As  we’ve discussed before , a good literature review needs to achieve a few very important objectives – it should:

• Demonstrate your knowledge of the research topic
• Identify the gaps in the literature and show how your research links to these
• Provide the foundation for your conceptual framework (if you have one)
• Inform your own  methodology and research design

To achieve this, your literature review needs a well-thought-out structure . Get the structure of your literature review chapter wrong and you’ll struggle to achieve these objectives. Don’t worry though – in this post, we’ll look at how to structure your literature review for maximum impact (and marks!).

But wait – is this the right time?

Deciding on the structure of your literature review should come towards the end of the literature review process – after you have collected and digested the literature, but before you start writing the chapter. 

In other words, you need to first develop a rich understanding of the literature before you even attempt to map out a structure. There’s no use trying to develop a structure before you’ve fully wrapped your head around the existing research.

Equally importantly, you need to have a structure in place before you start writing , or your literature review will most likely end up a rambling, disjointed mess. 

Importantly, don’t feel that once you’ve defined a structure you can’t iterate on it. It’s perfectly natural to adjust as you engage in the writing process. As we’ve discussed before , writing is a way of developing your thinking, so it’s quite common for your thinking to change – and therefore, for your chapter structure to change – as you write. 

Need a helping hand?

Like any other chapter in your thesis or dissertation, your literature review needs to have a clear, logical structure. At a minimum, it should have three essential components – an  introduction , a  body   and a  conclusion . 

Let’s take a closer look at each of these.

1: The Introduction Section

Just like any good introduction, the introduction section of your literature review should introduce the purpose and layout (organisation) of the chapter. In other words, your introduction needs to give the reader a taste of what’s to come, and how you’re going to lay that out. Essentially, you should provide the reader with a high-level roadmap of your chapter to give them a taste of the journey that lies ahead.

Here’s an example of the layout visualised in a literature review introduction:

Your introduction should also outline your topic (including any tricky terminology or jargon) and provide an explanation of the scope of your literature review – in other words, what you  will   and  won’t   be covering (the delimitations ). This helps ringfence your review and achieve a clear focus . The clearer and narrower your focus, the deeper you can dive into the topic (which is typically where the magic lies). 

Depending on the nature of your project, you could also present your stance or point of view at this stage. In other words, after grappling with the literature you’ll have an opinion about what the trends and concerns are in the field as well as what’s lacking. The introduction section can then present these ideas so that it is clear to examiners that you’re aware of how your research connects with existing knowledge .

2: The Body Section

The body of your literature review is the centre of your work. This is where you’ll present, analyse, evaluate and synthesise the existing research. In other words, this is where you’re going to earn (or lose) the most marks. Therefore, it’s important to carefully think about how you will organise your discussion to present it in a clear way. 

The body of your literature review should do just as the description of this chapter suggests. It should “review” the literature – in other words, identify, analyse, and synthesise it. So, when thinking about structuring your literature review, you need to think about which structural approach will provide the best “review” for your specific type of research and objectives (we’ll get to this shortly).

There are (broadly speaking)  three options  for organising your literature review.

Option 1: Chronological (according to date)

Organising the literature chronologically is one of the simplest ways to structure your literature review. You start with what was published first and work your way through the literature until you reach the work published most recently. Pretty straightforward.

The benefit of this option is that it makes it easy to discuss the developments and debates in the field as they emerged over time. Organising your literature chronologically also allows you to highlight how specific articles or pieces of work might have changed the course of the field – in other words, which research has had the most impact . Therefore, this approach is very useful when your research is aimed at understanding how the topic has unfolded over time and is often used by scholars in the field of history. That said, this approach can be utilised by anyone that wants to explore change over time .

For example , if a student of politics is investigating how the understanding of democracy has evolved over time, they could use the chronological approach to provide a narrative that demonstrates how this understanding has changed through the ages.

Here are some questions you can ask yourself to help you structure your literature review chronologically.

• What is the earliest literature published relating to this topic?
• How has the field changed over time? Why?
• What are the most recent discoveries/theories?

In some ways, chronology plays a part whichever way you decide to structure your literature review, because you will always, to a certain extent, be analysing how the literature has developed. However, with the chronological approach, the emphasis is very firmly on how the discussion has evolved over time , as opposed to how all the literature links together (which we’ll discuss next ).

Option 2: Thematic (grouped by theme)

The thematic approach to structuring a literature review means organising your literature by theme or category – for example, by independent variables (i.e. factors that have an impact on a specific outcome).

As you’ve been collecting and synthesising literature , you’ll likely have started seeing some themes or patterns emerging. You can then use these themes or patterns as a structure for your body discussion. The thematic approach is the most common approach and is useful for structuring literature reviews in most fields.

For example, if you were researching which factors contributed towards people trusting an organisation, you might find themes such as consumers’ perceptions of an organisation’s competence, benevolence and integrity. Structuring your literature review thematically would mean structuring your literature review’s body section to discuss each of these themes, one section at a time.

Here are some questions to ask yourself when structuring your literature review by themes:

• Are there any patterns that have come to light in the literature?
• What are the central themes and categories used by the researchers?
• Do I have enough evidence of these themes?

PS – you can see an example of a thematically structured literature review in our literature review sample walkthrough video here.

Option 3: Methodological

The methodological option is a way of structuring your literature review by the research methodologies used . In other words, organising your discussion based on the angle from which each piece of research was approached – for example, qualitative , quantitative or mixed  methodologies.

Structuring your literature review by methodology can be useful if you are drawing research from a variety of disciplines and are critiquing different methodologies. The point of this approach is to question  how  existing research has been conducted, as opposed to  what  the conclusions and/or findings the research were.

For example, a sociologist might centre their research around critiquing specific fieldwork practices. Their literature review will then be a summary of the fieldwork methodologies used by different studies.

Here are some questions you can ask yourself when structuring your literature review according to methodology:

• Which methodologies have been utilised in this field?
• Which methodology is the most popular (and why)?
• What are the strengths and weaknesses of the various methodologies?
• How can the existing methodologies inform my own methodology?

3: The Conclusion Section

Once you’ve completed the body section of your literature review using one of the structural approaches we discussed above, you’ll need to “wrap up” your literature review and pull all the pieces together to set the direction for the rest of your dissertation or thesis.

The conclusion is where you’ll present the key findings of your literature review. In this section, you should emphasise the research that is especially important to your research questions and highlight the gaps that exist in the literature. Based on this, you need to make it clear what you will add to the literature – in other words, justify your own research by showing how it will help fill one or more of the gaps you just identified.

Last but not least, if it’s your intention to develop a conceptual framework for your dissertation or thesis, the conclusion section is a good place to present this.

Example: Thematically Structured Review

In the video below, we unpack a literature review chapter so that you can see an example of a thematically structure review in practice.

Let’s Recap

In this article, we’ve  discussed how to structure your literature review for maximum impact. Here’s a quick recap of what  you need to keep in mind when deciding on your literature review structure:

• Just like other chapters, your literature review needs a clear introduction , body and conclusion .
• The introduction section should provide an overview of what you will discuss in your literature review.
• The body section of your literature review can be organised by chronology , theme or methodology . The right structural approach depends on what you’re trying to achieve with your research.
• The conclusion section should draw together the key findings of your literature review and link them to your research questions.

If you’re ready to get started, be sure to download our free literature review template to fast-track your chapter outline.

Psst… there’s more!

This post is an extract from our bestselling Udemy Course, Literature Review Bootcamp . If you want to work smart, you don't want to miss this .

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27 Comments

Great work. This is exactly what I was looking for and helps a lot together with your previous post on literature review. One last thing is missing: a link to a great literature chapter of an journal article (maybe with comments of the different sections in this review chapter). Do you know any great literature review chapters?

I agree with you Marin… A great piece

I agree with Marin. This would be quite helpful if you annotate a nicely structured literature from previously published research articles.

Awesome article for my research.

I thank you immensely for this wonderful guide

It is indeed thought and supportive work for the futurist researcher and students

Very educative and good time to get guide. Thank you

Great work, very insightful. Thank you.

Thanks for this wonderful presentation. My question is that do I put all the variables into a single conceptual framework or each hypothesis will have it own conceptual framework?

Thank you very much, very helpful

This is very educative and precise . Thank you very much for dropping this kind of write up .

Pheeww, so damn helpful, thank you for this informative piece.

I’m doing a research project topic ; stool analysis for parasitic worm (enteric) worm, how do I structure it, thanks.

comprehensive explanation. Help us by pasting the URL of some good “literature review” for better understanding.

great piece. thanks for the awesome explanation. it is really worth sharing. I have a little question, if anyone can help me out, which of the options in the body of literature can be best fit if you are writing an architectural thesis that deals with design?

I am doing a research on nanofluids how can l structure it?

Beautifully clear.nThank you!

Lucid! Thankyou!

Brilliant work, well understood, many thanks

I like how this was so clear with simple language 😊😊 thank you so much 😊 for these information 😊

Insightful. I was struggling to come up with a sensible literature review but this has been really helpful. Thank you!

You have given thought-provoking information about the review of the literature.

Thank you. It has made my own research better and to impart your work to students I teach

I learnt a lot from this teaching. It’s a great piece.

I am doing research on EFL teacher motivation for his/her job. How Can I structure it? Is there any detailed template, additional to this?

You are so cool! I do not think I’ve read through something like this before. So nice to find somebody with some genuine thoughts on this issue. Seriously.. thank you for starting this up. This site is one thing that is required on the internet, someone with a little originality!

I’m asked to do conceptual, theoretical and empirical literature, and i just don’t know how to structure it

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• How to Write a Literature Review | Guide, Examples, & Templates

How to Write a Literature Review | Guide, Examples, & Templates

Published on January 2, 2023 by Shona McCombes . Revised on September 11, 2023.

What is a literature review? A literature review is a survey of scholarly sources on a specific topic. It provides an overview of current knowledge, allowing you to identify relevant theories, methods, and gaps in the existing research that you can later apply to your paper, thesis, or dissertation topic .

There are five key steps to writing a literature review:

• Search for relevant literature
• Evaluate sources
• Identify themes, debates, and gaps
• Outline the structure
• Write your literature review

A good literature review doesn’t just summarize sources—it analyzes, synthesizes , and critically evaluates to give a clear picture of the state of knowledge on the subject.

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Table of contents

What is the purpose of a literature review, examples of literature reviews, 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

When you write a thesis , dissertation , or research paper , you will likely have to conduct a literature review to situate your research within existing knowledge. The literature review gives you a chance to:

• Demonstrate your familiarity with the topic and its scholarly context
• Develop a theoretical framework and methodology for your research
• Position your work in relation to other researchers and theorists
• Show how your research addresses a gap or contributes to a debate
• Evaluate the current state of research and demonstrate your knowledge of the scholarly debates around your topic.

Writing literature reviews is a particularly important skill if you want to apply for graduate school or pursue a career in research. We’ve written a step-by-step guide that you can follow below.

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Writing literature reviews can be quite challenging! A good starting point could be to look at some examples, depending on what kind of literature review you’d like to write.

• Example literature review #1: “Why Do People Migrate? A Review of the Theoretical Literature” ( Theoretical literature review about the development of economic migration theory from the 1950s to today.)
• Example literature review #2: “Literature review as a research methodology: An overview and guidelines” ( Methodological literature review about interdisciplinary knowledge acquisition and production.)
• Example literature review #3: “The Use of Technology in English Language Learning: A Literature Review” ( Thematic literature review about the effects of technology on language acquisition.)
• Example literature review #4: “Learners’ Listening Comprehension Difficulties in English Language Learning: A Literature Review” ( Chronological literature review about how the concept of listening skills has changed over time.)

You can also check out our templates with literature review examples and sample outlines at the links below.

Download Word doc Download Google doc

Before you begin searching for literature, you need a clearly defined topic .

If you are writing the literature review section of a dissertation or research paper, you will search for literature related to your research problem and questions .

Make a list of keywords

Start by creating a list of keywords related to your research question. Include each of the key concepts or variables you’re interested in, and list any synonyms and related terms. You can add to this list as you discover new keywords in the process of your literature search.

• Social media, Facebook, Instagram, Twitter, Snapchat, TikTok
• Body image, self-perception, self-esteem, mental health
• Generation Z, teenagers, adolescents, youth

Search for relevant sources

Use your keywords to begin searching for sources. Some useful databases to search for journals and articles include:

• Your university’s library catalogue
• Google Scholar
• Project Muse (humanities and social sciences)
• Medline (life sciences and biomedicine)
• EconLit (economics)
• Inspec (physics, engineering and computer science)

You can also use boolean operators to help narrow down your search.

Make sure to read the abstract to find out whether an article is relevant to your question. When you find a useful book or article, you can check the bibliography to find other relevant sources.

You likely won’t be able to read absolutely everything that has been written on your topic, so it will be necessary to evaluate which sources are most relevant to your research question.

For each publication, ask yourself:

• What question or problem is the author addressing?
• What are the key concepts and how are they defined?
• What are the key theories, models, and methods?
• Does the research use established frameworks or take an innovative approach?
• What are the results and conclusions of the study?
• How does the publication relate to other literature in the field? Does it confirm, add to, or challenge established knowledge?
• What are the strengths and weaknesses of the research?

Make sure the sources you use are credible , and make sure you read any landmark studies and major theories in your field of research.

You can use our template to summarize and evaluate sources you’re thinking about using. Click on either button below to download.

Take notes and cite your sources

As you read, you should also begin the writing process. Take notes that you can later incorporate into the text of your literature review.

It is important to keep track of your sources with citations to avoid plagiarism . It can be helpful to make an annotated bibliography , where you compile full citation information and write a paragraph of summary and analysis for each source. This helps you remember what you read and saves time later in the process.

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To begin organizing your literature review’s argument and structure, be sure you understand the connections and relationships between the sources you’ve read. Based on your reading and notes, you can look for:

• Trends and patterns (in theory, method or results): do certain approaches become more or less popular over time?
• Themes: what questions or concepts recur across the literature?
• Debates, conflicts and contradictions: where do sources disagree?
• Pivotal publications: are there any influential theories or studies that changed the direction of the field?
• Gaps: what is missing from the literature? Are there weaknesses that need to be addressed?

This step will help you work out the structure of your literature review and (if applicable) show how your own research will contribute to existing knowledge.

• Most research has focused on young women.
• There is an increasing interest in the visual aspects of social media.
• But there is still a lack of robust research on highly visual platforms like Instagram and Snapchat—this is a gap that you could address in your own research.

There are various approaches to organizing the body of a literature review. Depending on the length of your literature review, you can combine several of these strategies (for example, your overall structure might be thematic, but each theme is discussed chronologically).

Chronological

The simplest approach is to trace the development of the topic over time. However, if you choose this strategy, be careful to avoid simply listing and summarizing sources in order.

Try to analyze patterns, turning points and key debates that have shaped the direction of the field. Give your interpretation of how and why certain developments occurred.

If you have found some recurring central themes, you can organize your literature review into subsections that address different aspects of the topic.

For example, if you are reviewing literature about inequalities in migrant health outcomes, key themes might include healthcare policy, language barriers, cultural attitudes, legal status, and economic access.

Methodological

If you draw your sources from different disciplines or fields that use a variety of research methods , you might want to compare the results and conclusions that emerge from different approaches. For example:

• Look at what results have emerged in qualitative versus quantitative research
• Discuss how the topic has been approached by empirical versus theoretical scholarship
• Divide the literature into sociological, historical, and cultural sources

Theoretical

A literature review is often the foundation for a theoretical framework . You can use it to discuss various theories, models, and definitions of key concepts.

You might argue for the relevance of a specific theoretical approach, or combine various theoretical concepts to create a framework for your research.

Like any other academic text , your literature review should have an introduction , a main body, and a conclusion . What you include in each depends on the objective of your literature review.

The introduction should clearly establish the focus and purpose of the literature review.

Depending on the length of your literature review, you might want to divide the body into subsections. You can use a subheading for each theme, time period, or methodological approach.

As you write, you can follow these tips:

• Summarize and synthesize: give an overview of the main points of each source and combine them into a coherent whole
• Analyze and interpret: don’t just paraphrase other researchers — add your own interpretations where possible, discussing the significance of findings in relation to the literature as a whole
• Critically evaluate: mention the strengths and weaknesses of your sources
• Write in well-structured paragraphs: use transition words and topic sentences to draw connections, comparisons and contrasts

In the conclusion, you should summarize the key findings you have taken from the literature and emphasize their significance.

When you’ve finished writing and revising your literature review, don’t forget to proofread thoroughly before submitting. Not a language expert? Check out Scribbr’s professional proofreading services !

This article has been adapted into lecture slides that you can use to teach your students about writing a literature review.

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If you want to know more about the research process , methodology , research bias , or statistics , make sure to check out some of our other articles with explanations and examples.

• Sampling methods
• Simple random sampling
• Stratified sampling
• Cluster sampling
• Likert scales
• Reproducibility

 Statistics

• Null hypothesis
• Statistical power
• Probability distribution
• Effect size
• Poisson distribution

Research bias

• Optimism bias
• Cognitive bias
• Implicit bias
• Hawthorne effect
• Anchoring bias
• Explicit bias

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.

There are several reasons to conduct a literature review at the beginning of a research project:

• To familiarize yourself with the current state of knowledge on your topic
• To ensure that you’re not just repeating what others have already done
• To identify gaps in knowledge and unresolved problems that your research can address
• To develop your theoretical framework and methodology
• To provide an overview of the key findings and debates on the topic

Writing the literature review shows your reader how your work relates to existing research and what new insights it will contribute.

The literature review usually comes near the beginning of your thesis or dissertation . After the introduction , it grounds your research in a scholarly field and leads directly to your theoretical framework or methodology .

A literature review is a survey of credible sources on a topic, often used in dissertations , theses, and research papers . Literature reviews give an overview of knowledge on a subject, helping you identify relevant theories and methods, as well as gaps in existing research. Literature reviews are set up similarly to other  academic texts , with an introduction , a main body, and a conclusion .

An  annotated bibliography is a list of  source references that has a short description (called an annotation ) for each of the sources. It is often assigned as part of the research process for a  paper .  

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Writing a Literature Review

• Getting Started

Defining the topic

Limiting the scope.

• Finding the Literature
• Developing a Search Strategy
• Managing Your Research
• Writing the Review
• Systematic Reviews and Other Review Types
• Useful Books
• Useful Videos
• Useful Links
• Commonly Used Terms

Identifying a well-defined research question is the first step for writing a literature review. It should focus on something from the research field that needs to be explored, where there are gaps in the information. This will ensure that your contribution is valuable and that you are providing readers with a different angle or perspective on an issue or problem.

Your topic needs to be given careful consideration. A research question like “why are social networking sites harmful?” is too broad; there will be too much information to write a concise literature review. Change it to “how are online users experiencing or addressing privacy issues on Twitter and Facebook?" and it is more specific. It gives you a niche within the research field to focus on and explore.

Sometimes a broad topic can be narrowed by using one or more extra criteria, which can include:

• population group
• culture/ethnicity
• theoretical framework
• methodology (e.g., qualitative or quantitative, fieldwork/ethnography)

How you narrow the scope can be done in two broad ways, detailed in Developing a Search Strategy :

• add more search strands using AND to give fewer results (see Combining your terms: search operators )
• use "filters" in a database to eliminate results from outside those limits (see Using methodological search filters )
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• Last Updated: Oct 10, 2023 1:52 PM
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• What is a Literature Review? | Guide, Template, & Examples

What is a Literature Review? | Guide, Template, & Examples

Published on 22 February 2022 by Shona McCombes . Revised on 7 June 2022.

What is a literature review? A literature review is a survey of scholarly sources on a specific topic. It provides an overview of current knowledge, allowing you to identify relevant theories, methods, and gaps in the existing research.

There are five key steps to writing a literature review:

• Search for relevant literature
• Evaluate sources
• Identify themes, debates and gaps
• Outline the structure
• Write your literature review

A good literature review doesn’t just summarise sources – it analyses, synthesises, and critically evaluates to give a clear picture of the state of knowledge on the subject.

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Table of contents

Why write a literature review, examples of literature reviews, 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, frequently asked questions about literature reviews, introduction.

• Quick Run-through
• Step 1 & 2

When you write a dissertation or thesis, you will have to conduct a literature review to situate your research within existing knowledge. The literature review gives you a chance to:

• Demonstrate your familiarity with the topic and scholarly context
• Develop a theoretical framework and methodology for your research
• Position yourself in relation to other researchers and theorists
• Show how your dissertation addresses a gap or contributes to a debate

You might also have to write a literature review as a stand-alone assignment. In this case, the purpose is to evaluate the current state of research and demonstrate your knowledge of scholarly debates around a topic.

The content will look slightly different in each case, but the process of conducting a literature review follows the same steps. We’ve written a step-by-step guide that you can follow below.

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Writing literature reviews can be quite challenging! A good starting point could be to look at some examples, depending on what kind of literature review you’d like to write.

• Example literature review #1: “Why Do People Migrate? A Review of the Theoretical Literature” ( Theoretical literature review about the development of economic migration theory from the 1950s to today.)
• Example literature review #2: “Literature review as a research methodology: An overview and guidelines” ( Methodological literature review about interdisciplinary knowledge acquisition and production.)
• Example literature review #3: “The Use of Technology in English Language Learning: A Literature Review” ( Thematic literature review about the effects of technology on language acquisition.)
• Example literature review #4: “Learners’ Listening Comprehension Difficulties in English Language Learning: A Literature Review” ( Chronological literature review about how the concept of listening skills has changed over time.)

You can also check out our templates with literature review examples and sample outlines at the links below.

Download Word doc Download Google doc

Before you begin searching for literature, you need a clearly defined topic .

If you are writing the literature review section of a dissertation or research paper, you will search for literature related to your research objectives and questions .

If you are writing a literature review as a stand-alone assignment, you will have to choose a focus and develop a central question to direct your search. Unlike a dissertation research question, this question has to be answerable without collecting original data. You should be able to answer it based only on a review of existing publications.

Make a list of keywords

Start by creating a list of keywords related to your research topic. Include each of the key concepts or variables you’re interested in, and list any synonyms and related terms. You can add to this list if you discover new keywords in the process of your literature search.

• Social media, Facebook, Instagram, Twitter, Snapchat, TikTok
• Body image, self-perception, self-esteem, mental health
• Generation Z, teenagers, adolescents, youth

Search for relevant sources

Use your keywords to begin searching for sources. Some databases to search for journals and articles include:

• Your university’s library catalogue
• Google Scholar
• Project Muse (humanities and social sciences)
• Medline (life sciences and biomedicine)
• EconLit (economics)
• Inspec (physics, engineering and computer science)

You can use boolean operators to help narrow down your search:

Read the abstract to find out whether an article is relevant to your question. When you find a useful book or article, you can check the bibliography to find other relevant sources.

To identify the most important publications on your topic, take note of recurring citations. If the same authors, books or articles keep appearing in your reading, make sure to seek them out.

You probably won’t be able to read absolutely everything that has been written on the topic – you’ll have to evaluate which sources are most relevant to your questions.

For each publication, ask yourself:

• What question or problem is the author addressing?
• What are the key concepts and how are they defined?
• What are the key theories, models and methods? Does the research use established frameworks or take an innovative approach?
• What are the results and conclusions of the study?
• How does the publication relate to other literature in the field? Does it confirm, add to, or challenge established knowledge?
• How does the publication contribute to your understanding of the topic? What are its key insights and arguments?
• What are the strengths and weaknesses of the research?

Make sure the sources you use are credible, and make sure you read any landmark studies and major theories in your field of research.

You can find out how many times an article has been cited on Google Scholar – a high citation count means the article has been influential in the field, and should certainly be included in your literature review.

The scope of your review will depend on your topic and discipline: in the sciences you usually only review recent literature, but in the humanities you might take a long historical perspective (for example, to trace how a concept has changed in meaning over time).

Remember that you can use our template to summarise and evaluate sources you’re thinking about using!

Take notes and cite your sources

As you read, you should also begin the writing process. Take notes that you can later incorporate into the text of your literature review.

It’s important to keep track of your sources with references to avoid plagiarism . It can be helpful to make an annotated bibliography, where you compile full reference information and write a paragraph of summary and analysis for each source. This helps you remember what you read and saves time later in the process.

You can use our free APA Reference Generator for quick, correct, consistent citations.

Prevent plagiarism, run a free check.

To begin organising your literature review’s argument and structure, you need to understand the connections and relationships between the sources you’ve read. Based on your reading and notes, you can look for:

• Trends and patterns (in theory, method or results): do certain approaches become more or less popular over time?
• Themes: what questions or concepts recur across the literature?
• Debates, conflicts and contradictions: where do sources disagree?
• Pivotal publications: are there any influential theories or studies that changed the direction of the field?
• Gaps: what is missing from the literature? Are there weaknesses that need to be addressed?

This step will help you work out the structure of your literature review and (if applicable) show how your own research will contribute to existing knowledge.

• Most research has focused on young women.
• There is an increasing interest in the visual aspects of social media.
• But there is still a lack of robust research on highly-visual platforms like Instagram and Snapchat – this is a gap that you could address in your own research.

There are various approaches to organising the body of a literature review. You should have a rough idea of your strategy before you start writing.

Depending on the length of your literature review, you can combine several of these strategies (for example, your overall structure might be thematic, but each theme is discussed chronologically).

Chronological

The simplest approach is to trace the development of the topic over time. However, if you choose this strategy, be careful to avoid simply listing and summarising sources in order.

Try to analyse patterns, turning points and key debates that have shaped the direction of the field. Give your interpretation of how and why certain developments occurred.

If you have found some recurring central themes, you can organise your literature review into subsections that address different aspects of the topic.

For example, if you are reviewing literature about inequalities in migrant health outcomes, key themes might include healthcare policy, language barriers, cultural attitudes, legal status, and economic access.

Methodological

If you draw your sources from different disciplines or fields that use a variety of research methods , you might want to compare the results and conclusions that emerge from different approaches. For example:

• Look at what results have emerged in qualitative versus quantitative research
• Discuss how the topic has been approached by empirical versus theoretical scholarship
• Divide the literature into sociological, historical, and cultural sources

Theoretical

A literature review is often the foundation for a theoretical framework . You can use it to discuss various theories, models, and definitions of key concepts.

You might argue for the relevance of a specific theoretical approach, or combine various theoretical concepts to create a framework for your research.

Like any other academic text, your literature review should have an introduction , a main body, and a conclusion . What you include in each depends on the objective of your literature review.

The introduction should clearly establish the focus and purpose of the literature review.

If you are writing the literature review as part of your dissertation or thesis, reiterate your central problem or research question and give a brief summary of the scholarly context. You can emphasise the timeliness of the topic (“many recent studies have focused on the problem of x”) or highlight a gap in the literature (“while there has been much research on x, few researchers have taken y into consideration”).

Depending on the length of your literature review, you might want to divide the body into subsections. You can use a subheading for each theme, time period, or methodological approach.

As you write, make sure to follow these tips:

• Summarise and synthesise: give an overview of the main points of each source and combine them into a coherent whole.
• Analyse and interpret: don’t just paraphrase other researchers – add your own interpretations, discussing the significance of findings in relation to the literature as a whole.
• Critically evaluate: mention the strengths and weaknesses of your sources.
• Write in well-structured paragraphs: use transitions and topic sentences to draw connections, comparisons and contrasts.

In the conclusion, you should summarise the key findings you have taken from the literature and emphasise their significance.

If the literature review is part of your dissertation or thesis, reiterate how your research addresses gaps and contributes new knowledge, or discuss how you have drawn on existing theories and methods to build a framework for your research. This can lead directly into your methodology section.

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 dissertation , thesis, research paper , or proposal .

There are several reasons to conduct a literature review at the beginning of a research project:

• To familiarise yourself with the current state of knowledge on your topic
• To ensure that you’re not just repeating what others have already done
• To identify gaps in knowledge and unresolved problems that your research can address
• To develop your theoretical framework and methodology
• To provide an overview of the key findings and debates on the topic

Writing the literature review shows your reader how your work relates to existing research and what new insights it will contribute.

The literature review usually comes near the beginning of your  dissertation . After the introduction , it grounds your research in a scholarly field and leads directly to your theoretical framework or methodology .

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Writing a Literature Review

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Identifying a well-defined research topic is the first step for writing a literature review. The topic should cover something from the research field that needs to be explored. This will ensure that your contribution will be valuable, that you are providing readers with a different angle or perspective on an issue or problem.

Ideally, your topic should tackle or explore a problem that is just the right size. A topic like “mothers and postpartum depression” is too broad; there will be too much information out there to write a concise literature review. However, a topic such as “maternal postpartum self-criticism and anger” looks at a problem faced by women who are experiencing the so-called baby blues. This gives you a niche within the research field to focus on and explore.

Often a broad topic can be narrowed by adding one or more criteria, which can include:

• population group
• culture/ethnicity
• theoretical framework
• methodology (e.g., qualitative or quantitative, fieldwork/ethnography)
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What Is a Systematic Review?

Regular literature reviews are simply summaries of the literature on a particular topic. A systematic review, however, is a comprehensive literature review conducted to answer a specific research question. Authors of a systematic review aim to find, code, appraise, and synthesize all of the previous research on their question in an unbiased and well-documented manner. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) outline the minimum amount of information that needs to be reported at the conclusion of a systematic review project. 

Other types of what are known as "evidence syntheses," such as scoping, rapid, and integrative reviews, have varying methodologies. While systematic reviews originated with and continue to be a popular publication type in medicine and other health sciences fields, more and more researchers in other disciplines are choosing to conduct evidence syntheses. 

This guide will walk you through the major steps of a systematic review and point you to key resources including Covidence, a systematic review project management tool. For help with systematic reviews and other major literature review projects, please send us an email at  [email protected] .

Getting Help with Reviews

Organization such as the Institute of Medicine recommend that you consult a librarian when conducting a systematic review. Librarians at the University of Nevada, Reno can help you:

• Understand best practices for conducting systematic reviews and other evidence syntheses in your discipline
• Choose and formulate a research question
• Decide which review type (e.g., systematic, scoping, rapid, etc.) is the best fit for your project
• Determine what to include and where to register a systematic review protocol
• Select search terms and develop a search strategy
• Identify databases and platforms to search
• Find the full text of articles and other sources
• Become familiar with free citation management (e.g., EndNote, Zotero)
• Get access to you and help using Covidence, a systematic review project management tool

Doing a Systematic Review

• Plan - This is the project planning stage. You and your team will need to develop a good research question, determine the type of review you will conduct (systematic, scoping, rapid, etc.), and establish the inclusion and exclusion criteria (e.g., you're only going to look at studies that use a certain methodology). All of this information needs to be included in your protocol. You'll also need to ensure that the project is viable - has someone already done a systematic review on this topic? Do some searches and check the various protocol registries to find out. 
• Identify - Next, a comprehensive search of the literature is undertaken to ensure all studies that meet the predetermined criteria are identified. Each research question is different, so the number and types of databases you'll search - as well as other online publication venues - will vary. Some standards and guidelines specify that certain databases (e.g., MEDLINE, EMBASE) should be searched regardless. Your subject librarian can help you select appropriate databases to search and develop search strings for each of those databases.  
• Evaluate - In this step, retrieved articles are screened and sorted using the predetermined inclusion and exclusion criteria. The risk of bias for each included study is also assessed around this time. It's best if you import search results into a citation management tool (see below) to clean up the citations and remove any duplicates. You can then use a tool like Rayyan (see below) to screen the results. You should begin by screening titles and abstracts only, and then you'll examine the full text of any remaining articles. Each study should be reviewed by a minimum of two people on the project team. 
• Collect - Each included study is coded and the quantitative or qualitative data contained in these studies is then synthesized. You'll have to either find or develop a coding strategy or form that meets your needs. 
• Explain - The synthesized results are articulated and contextualized. What do the results mean? How have they answered your research question?
• Summarize - The final report provides a complete description of the methods and results in a clear, transparent fashion. 

Adapted from

Types of reviews, systematic review.

These types of studies employ a systematic method to analyze and synthesize the results of numerous studies. "Systematic" in this case means following a strict set of steps - as outlined by entities like PRISMA and the Institute of Medicine - so as to make the review more reproducible and less biased. Consistent, thorough documentation is also key. Reviews of this type are not meant to be conducted by an individual but rather a (small) team of researchers. Systematic reviews are widely used in the health sciences, often to find a generalized conclusion from multiple evidence-based studies. 

Meta-Analysis

A systematic method that uses statistics to analyze the data from numerous studies. The researchers combine the data from studies with similar data types and analyze them as a single, expanded dataset. Meta-analyses are a type of systematic review.

Scoping Review

A scoping review employs the systematic review methodology to explore a broader topic or question rather than a specific and answerable one, as is generally the case with a systematic review. Authors of these types of reviews seek to collect and categorize the existing literature so as to identify any gaps.

Rapid Review

Rapid reviews are systematic reviews conducted under a time constraint. Researchers make use of workarounds to complete the review quickly (e.g., only looking at English-language publications), which can lead to a less thorough and more biased review. 

Narrative Review

A traditional literature review that summarizes and synthesizes the findings of numerous original research articles. The purpose and scope of narrative literature reviews vary widely and do not follow a set protocol. Most literature reviews are narrative reviews. 

Umbrella Review

Umbrella reviews are, essentially, systematic reviews of systematic reviews. These compile evidence from multiple review studies into one usable document. 

Grant, Maria J., and Andrew Booth. “A Typology of Reviews: An Analysis of 14 Review Types and Associated Methodologies.” Health Information & Libraries Journal , vol. 26, no. 2, 2009, pp. 91-108. doi: 10.1111/j.1471-1842.2009.00848.x .

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Literature reviews, what is a literature review, learning more about how to do a literature review.

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A literature review is a review and synthesis of existing research on a topic or research question. A literature review is meant to analyze the scholarly literature, make connections across writings and identify strengths, weaknesses, trends, and missing conversations. A literature review should address different aspects of a topic as it relates to your research question. A literature review goes beyond a description or summary of the literature you have read. 

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What is a literature review?

A literature review is an integrated analysis -- not just a summary-- of scholarly writings and other relevant evidence related directly to your research question.  That is, it represents a synthesis of the evidence that provides background information on your topic and shows a association between the evidence and your research question.

A literature review may be a stand alone work or the introduction to a larger research paper, depending on the assignment.  Rely heavily on the guidelines your instructor has given you.

Why is it important?

A literature review is important because it:

• Explains the background of research on a topic.
• Demonstrates why a topic is significant to a subject area.
• Discovers relationships between research studies/ideas.
• Identifies major themes, concepts, and researchers on a topic.
• Identifies critical gaps and points of disagreement.
• Discusses further research questions that logically come out of the previous studies.

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1. Choose a topic. Define your research question.

Your literature review should be guided by your central research question.  The literature represents background and research developments related to a specific research question, interpreted and analyzed by you in a synthesized way.

• Make sure your research question is not too broad or too narrow.  Is it manageable?
• Begin writing down terms that are related to your question. These will be useful for searches later.
• If you have the opportunity, discuss your topic with your professor and your class mates.

2. Decide on the scope of your review

How many studies do you need to look at? How comprehensive should it be? How many years should it cover? 

• This may depend on your assignment.  How many sources does the assignment require?

3. Select the databases you will use to conduct your searches.

Make a list of the databases you will search. 

Where to find databases:

• use the tabs on this guide
• Find other databases in the Nursing Information Resources web page
• More on the Medical Library web page
• ... and more on the Yale University Library web page

4. Conduct your searches to find the evidence. Keep track of your searches.

• Use the key words in your question, as well as synonyms for those words, as terms in your search. Use the database tutorials for help.
• Save the searches in the databases. This saves time when you want to redo, or modify, the searches. It is also helpful to use as a guide is the searches are not finding any useful results.
• Review the abstracts of research studies carefully. This will save you time.
• Use the bibliographies and references of research studies you find to locate others.
• Check with your professor, or a subject expert in the field, if you are missing any key works in the field.
• Ask your librarian for help at any time.
• Use a citation manager, such as EndNote as the repository for your citations. See the EndNote tutorials for help.

Review the literature

Some questions to help you analyze the research:

• What was the research question of the study you are reviewing? What were the authors trying to discover?
• Was the research funded by a source that could influence the findings?
• What were the research methodologies? Analyze its literature review, the samples and variables used, the results, and the conclusions.
• Does the research seem to be complete? Could it have been conducted more soundly? What further questions does it raise?
• If there are conflicting studies, why do you think that is?
• How are the authors viewed in the field? Has this study been cited? If so, how has it been analyzed?

Tips: 

• Review the abstracts carefully.  
• Keep careful notes so that you may track your thought processes during the research process.
• Create a matrix of the studies for easy analysis, and synthesis, across all of the studies.
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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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Literature Reviews

• What is a literature review?
• Steps in the Literature Review Process
• Define your research question
• Determine inclusion and exclusion criteria
• Choose databases and search
• Review Results
• Synthesize Results
• Analyze Results
• Librarian Support

What is a Literature Review?

A literature or narrative review is a comprehensive review and analysis of the published literature on a specific topic or research question. The literature that is reviewed contains: books, articles, academic articles, conference proceedings, association papers, and dissertations. It contains the most pertinent studies and points to important past and current research and practices. It provides background and context, and shows how your research will contribute to the field. 

A literature review should: 

• Provide a comprehensive and updated review of the literature;
• Explain why this review has taken place;
• Articulate a position or hypothesis;
• Acknowledge and account for conflicting and corroborating points of view

From  S age Research Methods

Purpose of a Literature Review

A literature review can be written as an introduction to a study to:

• Demonstrate how a study fills a gap in research
• Compare a study with other research that's been done

Or it can be a separate work (a research article on its own) which:

• Organizes or describes a topic
• Describes variables within a particular issue/problem

Limitations of a Literature Review

Some of the limitations of a literature review are:

• It's a snapshot in time. Unlike other reviews, this one has beginning, a middle and an end. There may be future developments that could make your work less relevant.
• It may be too focused. Some niche studies may miss the bigger picture.
• It can be difficult to be comprehensive. There is no way to make sure all the literature on a topic was considered.
• It is easy to be biased if you stick to top tier journals. There may be other places where people are publishing exemplary research. Look to open access publications and conferences to reflect a more inclusive collection. Also, make sure to include opposing views (and not just supporting evidence).

Source: Grant, Maria J., and Andrew Booth. “A Typology of Reviews: An Analysis of 14 Review Types and Associated Methodologies.” Health Information & Libraries Journal, vol. 26, no. 2, June 2009, pp. 91–108. Wiley Online Library, doi:10.1111/j.1471-1842.2009.00848.x.

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For help in other subject areas, please see the guide to library specialists by subject .

Periodically, UT Libraries runs a workshop covering the basics and library support for literature reviews. While we try to offer these once per academic year, we find providing the recording to be helpful to community members who have missed the session. Following is the most recent recording of the workshop, Conducting a Literature Review. To view the recording, a UT login is required.

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Cochrane Training

Chapter 2: determining the scope of the review and the questions it will address.

James Thomas, Dylan Kneale, Joanne E McKenzie, Sue E Brennan, Soumyadeep Bhaumik

Key Points:

• Systematic reviews should address answerable questions and fill important gaps in knowledge.
• Developing good review questions takes time, expertise and engagement with intended users of the review.
• Cochrane Reviews can focus on broad questions, or be more narrowly defined. There are advantages and disadvantages of each.
• Logic models are a way of documenting how interventions, particularly complex interventions, are intended to ‘work’, and can be used to refine review questions and the broader scope of the review.
• Using priority-setting exercises, involving relevant stakeholders, and ensuring that the review takes account of issues relating to equity can be strategies for ensuring that the scope and focus of reviews address the right questions.

Cite this chapter as: Thomas J, Kneale D, McKenzie JE, Brennan SE, Bhaumik S. Chapter 2: Determining the scope of the review and the questions it will address. In: Higgins JPT, Thomas J, Chandler J, Cumpston M, Li T, Page MJ, Welch VA (editors). Cochrane Handbook for Systematic Reviews of Interventions version 6.4 (updated August 2023). Cochrane, 2023. Available from www.training.cochrane.org/handbook .

2.1 Rationale for well-formulated questions

As with any research, the first and most important decision in preparing a systematic review is to determine its focus. This is best done by clearly framing the questions the review seeks to answer. The focus of any Cochrane Review should be on questions that are important to people making decisions about health or health care. These decisions will usually need to take into account both the benefits and harms of interventions (see MECIR Box 2.1.a ). Good review questions often take time to develop, requiring engagement with not only the subject area, but with a wide group of stakeholders (Section 2.4.2 ).

Well-formulated questions will guide many aspects of the review process, including determining eligibility criteria, searching for studies, collecting data from included studies, structuring the syntheses and presenting findings (Cooper 1984, Hedges 1994, Oliver et al 2017) . In Cochrane Reviews, questions are stated broadly as review ‘Objectives’, and operationalized in terms of the studies that will be eligible to answer those questions as ‘Criteria for considering studies for this review’. As well as focusing review conduct, the contents of these sections are used by readers in their initial assessments of whether the review is likely to be directly relevant to the issues they face.

The FINER criteria have been proposed as encapsulating the issues that should be addressed when developing research questions. These state that questions should be F easible, I nteresting, N ovel, E thical, and R elevant (Cummings et al 2007). All of these criteria raise important issues for consideration at the outset of a review and should be borne in mind when questions are formulated.

A feasible review is one that asks a question that the author team is capable of addressing using the evidence available. Issues concerning the breadth of a review are discussed in Section 2.3.1 , but in terms of feasibility it is important not to ask a question that will result in retrieving unmanageable quantities of information; up-front scoping work will help authors to define sensible boundaries for their reviews. Likewise, while it can be useful to identify gaps in the evidence base, review authors and stakeholders should be aware of the possibility of asking a question that may not be answerable using the existing evidence (i.e. that will result in an ‘empty’ review, see also Section 2.5.3 ).

Embarking on a review that authors are interested in is important because reviews are a significant undertaking and review authors need sufficient commitment to see the work through to its conclusion.

A novel review will address a genuine gap in knowledge, so review authors should be aware of any related or overlapping reviews. This reduces duplication of effort, and also ensures that authors understand the wider research context to which their review will contribute. Authors should check for pre-existing syntheses in the published research literature and also for ongoing reviews in the PROSPERO register of systematic reviews before beginning their own review.

Given the opportunity cost involved in undertaking an activity as demanding as a systematic review, authors should ensure that their work is relevant by: (i) involving relevant stakeholders in defining its focus and the questions it will address; and (ii) writing up the review in such a way as to facilitate the translation of its findings to inform decisions. The GRADE framework aims to achieve this, and should be considered throughout the review process, not only when it is being written up (see Chapter 14 and Chapter 15 ).

Consideration of opportunity costs is also relevant in terms of the ethics of conducting a review, though ethical issues should also be considered primarily in terms of the questions that are prioritized for answering and the way that they are framed. Research questions are often not value-neutral, and the way that a given problem is approached can have political implications which can result in, for example, the widening of health inequalities (whether intentional or not). These issues are explored in Section 2.4.3 and Chapter 16 .

MECIR Box 2.1.a Relevant expectations for conduct of intervention reviews

2.2 Aims of reviews of interventions

Systematic reviews can address any question that can be answered by a primary research study. This Handbook focuses on a subset of all possible review questions: the impact of intervention(s) implemented within a specified human population. Even within these limits, systematic reviews examining the effects of intervention(s) can vary quite markedly in their aims. Some will focus specifically on evidence of an effect of an intervention compared with a specific alternative, whereas others may examine a range of different interventions. Reviews that examine multiple interventions and aim to identify which might be the most effective can be broader and more challenging than those looking at single interventions. These can also be the most useful for end users, where decision making involves selecting from a number of intervention options. The incorporation of network meta-analysis as a core method in this edition of the Handbook (see Chapter 11 ) reflects the growing importance of these types of reviews.

As well as looking at the balance of benefit and harm that can be attributed to a given intervention, reviews within the ambit of this Handbook might also aim to investigate the relationship between the size of an intervention effect and other characteristics, such as aspects of the population, the intervention itself, how the outcome is measured, or the methodology of the primary research studies included. Such approaches might be used to investigate which components of multi-component interventions are more or less important or essential (and when). While it is not always necessary to know how an intervention achieves its effect for it to be useful, many reviews will aim to articulate an intervention’s mechanisms of action (see Section 2.5.1 ), either by making this an explicit aim of the review itself (see Chapter 17 and Chapter 21 ), or when describing the scope of the review. Understanding how an intervention works (or is intended to work) can be an important aid to decision makers in assessing the applicability of the review to their situation. These investigations can be assisted by the incorporation of results from process evaluations conducted alongside trials (see Chapter 21 ). Further, many decisions in policy and practice are at least partially constrained by the resource available, so review authors often need to consider the economic context of interventions (see Chapter 20 ).

2.3 Defining the scope of a review question

Studies comparing healthcare interventions, notably randomized trials, use the outcomes of participants to compare the effects of different interventions. Statistical syntheses (e.g. meta-analysis) focus on comparisons of interventions, such as a new intervention versus a control intervention (which may represent conditions of usual practice or care), or the comparison of two competing interventions. Throughout the Handbook we use the terminology experimental intervention versus comparator intervention. This implies a need to identify one of the interventions as experimental, and is used only for convenience since all methods apply to both controlled and head-to-head comparisons. The contrast between the outcomes of two groups treated differently is known as the ‘effect’, the ‘treatment effect’ or the ‘intervention effect’; we generally use the last of these throughout the Handbook .

A statement of the review’s objectives should begin with a precise statement of the primary objective, ideally in a single sentence ( MECIR Box 2.3.a ). Where possible the style should be of the form ‘To assess the effects of [ intervention or comparison ] for [ health problem ] in [ types of people, disease or problem and setting if specified ]’. This might be followed by one or more secondary objectives, for example relating to different participant groups, different comparisons of interventions or different outcome measures. The detailed specification of the review question(s) requires consideration of several key components (Richardson et al 1995, Counsell 1997) which can often be encapsulated by the ‘PICO’ mnemonic, an acronym for P opulation, I ntervention, C omparison(s) and O utcome. Equal emphasis in addressing, and equal precision in defining, each PICO component is not necessary. For example, a review might concentrate on competing interventions for a particular stage of breast cancer, with stage and severity of the disease being defined very precisely; or alternately focus on a particular drug for any stage of breast cancer, with the treatment formulation being defined very precisely.

Throughout the Handbook we make a distinction between three different stages in the review at which the PICO construct might be used. This division is helpful for understanding the decisions that need to be made:

• The review PICO (planned at the protocol stage) is the PICO on which eligibility of studies is based (what will be included and what excluded from the review).
• The PICO for each synthesis (also planned at the protocol stage) defines the question that each specific synthesis aims to answer, determining how the synthesis will be structured, specifying planned comparisons (including intervention and comparator groups, any grouping of outcome and population subgroups).
• The PICO of the included studies (determined at the review stage) is what was actually investigated in the included studies.

Reaching the point where it is possible to articulate the review’s objectives in the above form – the review PICO – requires time and detailed discussion between potential authors and users of the review. It is important that those involved in developing the review’s scope and questions have a good knowledge of the practical issues that the review will address as well as the research field to be synthesized. Developing the questions is a critical part of the research process. As such, there are methodological issues to bear in mind, including: how to determine which questions are most important to answer; how to engage stakeholders in question formulation; how to account for changes in focus as the review progresses; and considerations about how broad (or narrow) a review should be.

MECIR Box 2.3 . a Relevant expectations for conduct of intervention reviews

2.3.1 Broad versus narrow reviews

The questions addressed by a review may be broad or narrow in scope. For example, a review might address a broad question regarding whether antiplatelet agents in general are effective in preventing all thrombotic events in humans. Alternatively, a review might address whether a particular antiplatelet agent, such as aspirin, is effective in decreasing the risks of a particular thrombotic event, stroke, in elderly persons with a previous history of stroke. Increasingly, reviews are becoming broader, aiming, for example, to identify which intervention – out of a range of treatment options – is most effective, or to investigate how an intervention varies depending on implementation and participant characteristics.

Overviews of reviews (see  Chapter V ), in which multiple reviews are summarized, can be one way of addressing the need for breadth when synthesizing the evidence base, since they can summarize multiple reviews of different interventions for the same condition, or multiple reviews of the same intervention for different types of participants. It may be considered desirable to plan a series of reviews with a relatively narrow scope, alongside an Overview to summarize their findings. Alternatively, it may be more useful – particularly given the growth in support for network meta-analysis – to combine comparisons of different treatment options within the same review (see Chapter 11 ). When deciding whether or not an overview might be the most appropriate approach, review authors should take account of the breadth of the question being asked and the resources available. Some questions are simply too broad for a review of all relevant primary research to be practicable, and if a field has sufficient high-quality reviews, then the production of another review of primary research that duplicates the others might not be a sensible use of resources.

Some of the advantages and disadvantages of broad and narrow reviews are summarized in Table 2.3.a . While having a broad scope in terms of the range of participants has the potential to increase generalizability, the extent to which findings are ultimately applicable to broader (or different) populations will depend on the participants who have actually been recruited into research studies. Likewise, heterogeneity can be a disadvantage when the expectation is for homogeneity of effects between studies, but an advantage when the review question seeks to understand differential effects (see Chapter 10 ).A distinction should be drawn between the scope of a review and the precise questions within, since it is possible to have a broad review that addresses quite narrow questions. In the antiplatelet agents for preventing thrombotic events example, a systematic review with a broad scope might include all available treatments. Rather than combining all the studies into one comparison though, specific treatments would be compared with one another in separate comparisons, thus breaking a heterogeneous set of treatments into narrower, more homogenous groups. This relates to the three levels of PICO, outlined in Section 2.3 . The review PICO defines the broad scope of the review, and the PICO for comparison defines the specific treatments that will be compared with one another; Chapter 3 elaborates on the use of PICOs.

In practice, a Cochrane Review may start (or have started) with a broad scope, and be divided up into narrower reviews as evidence accumulates and the original review becomes unwieldy. This may be done for practical and logistical reasons, for example to make updating easier as well as to make it easier for readers to see which parts of the evidence base are changing. Individual review authors must decide if there are instances where splitting a broader focused review into a series of more narrowly focused reviews is appropriate and implement appropriate methods to achieve this. If a major change is to be undertaken, such as splitting a broad review into a series of more narrowly focused reviews, a new protocol must be written for each of the component reviews that documents the eligibility criteria for each one.

Ultimately, the selected breadth of a review depends upon multiple factors including perspectives regarding a question’s relevance and potential impact; supporting theoretical, biologic and epidemiological information; the potential generalizability and validity of answers to the questions; and available resources. As outlined in Section 2.4.2 , authors should consider carefully the needs of users of the review and the context(s) in which they expect the review to be used when determining the most optimal scope for their review.

Table 2.3.a Some advantages and disadvantages of broad versus narrow reviews

2.3.2 ‘Lumping’ versus ‘splitting’

It is important not to confuse the issue of the breadth of the review (determined by the review PICO) with concerns about between-study heterogeneity and the legitimacy of combining results from diverse studies in the same analysis (determined by the PICOs for comparison).

Broad reviews have been criticized as ‘mixing apples and oranges’, and one of the inventors of meta-analysis, Gene Glass, has responded “Of course it mixes apples and oranges… comparing apples and oranges is the only endeavour worthy of true scientists; comparing apples to apples is trivial” (Glass 2015). In fact, the two concepts (‘broad reviews’ and ‘mixing apples and oranges’) are different issues. Glass argues that broad reviews, with diverse studies, provide the opportunity to ask interesting questions about the reasons for differential intervention effects.

The ‘apples and oranges’ critique refers to the inappropriate mixing of studies within a single comparison, where the purpose is to estimate an average effect. In situations where good biologic or sociological evidence suggests that various formulations of an intervention behave very differently or that various definitions of the condition of interest are associated with markedly different effects of the intervention, the uncritical aggregation of results from quite different interventions or populations/settings may well be questionable.

Unfortunately, determining the situations where studies are similar enough to combine with one another is not always straightforward, and it can depend, to some extent, on the question being asked. While the decision is sometimes characterized as ‘lumping’ (where studies are combined in the same analysis) or ‘splitting’ (where they are not) (Squires et al 2013), it is better to consider these issues on a continuum, with reviews that have greater variation in the types of included interventions, settings and populations, and study designs being towards the ‘lumped’ end, and those that include little variation in these elements being towards the ‘split’ end (Petticrew and Roberts 2006).

While specification of the review PICO sets the boundary for the inclusion and exclusion of studies, decisions also need to be made when planning the PICO for the comparisons to be made in the analysis as to whether they aim to address broader (‘lumped’) or narrower (‘split’) questions (Caldwell and Welton 2016). The degree of ‘lumping’ in the comparisons will be primarily driven by the review’s objectives, but will sometimes be dictated by the availability of studies (and data) for a particular comparison (see Chapter 9 for discussion of the latter). The former is illustrated by a Cochrane Review that examined the effects of newer-generation antidepressants for depressive disorders in children and adolescents (Hetrick et al 2012).

Newer-generation antidepressants include multiple different compounds (e.g. paroxetine, fluoxetine). The objectives of this review were to (i) estimate the overall effect of newer-generation antidepressants on depression, (ii) estimate the effect of each compound, and (iii) examine whether the compound type and age of the participants (children versus adolescents) is associated with the intervention effect. Objective (i) addresses a broad, ‘in principle’ (Caldwell and Welton 2016), question of whether newer-generation antidepressants improve depression, where the different compounds are ‘lumped’ into a single comparison. Objective (ii) seeks to address narrower, ‘split’, questions that investigate the effect of each compound on depression separately. Answers to both questions can be identified by setting up separate comparisons for each compound, or by subgrouping the ‘lumped’ comparison by compound ( Chapter 10, Section 10.11.2 ). Objective (iii) seeks to explore factors that explain heterogeneity among the intervention effects, or equivalently, whether the intervention effect varies by the factor. This can be examined using subgroup analysis or meta-regression ( Chapter 10, Section 10.11 ) but, in the case of intervention types, is best achieved using network meta-analysis (see Chapter 11 ).

There are various advantages and disadvantages to bear in mind when defining the PICO for the comparison and considering whether ‘lumping’ or ‘splitting’ is appropriate. Lumping allows for the investigation of factors that may explain heterogeneity. Results from these investigations may provide important leads as to whether an intervention operates differently in, for example, different populations (such as in children and adolescents in the example above). Ultimately, this type of knowledge is useful for clinical decision making. However, lumping is likely to introduce heterogeneity, which will not always be explained by a priori specified factors, and this may lead to a combined effect that is clinically difficult to interpret and implement. For example, when multiple intervention types are ‘lumped’ in one comparison (as in objective (i) above), and there is unexplained heterogeneity, the combined intervention effect would not enable a clinical decision as to which intervention should be selected. Splitting comparisons carries its own risk of there being too few studies to yield a useful synthesis. Inevitably, some degree of aggregation across the PICO elements is required for a meta-analysis to be undertaken (Caldwell and Welton 2016).

2.4 Ensuring the review addresses the right questions

Since systematic reviews are intended for use in healthcare decision making, review teams should ensure not only the application of robust methodology, but also that the review question is meaningful for healthcare decision making. Two approaches are discussed below:

• Using results from existing research priority-setting exercises to define the review question.
• In the absence of, or in addition to, existing research priority-setting exercises, engaging with stakeholders to define review questions and establish their relevance to policy and practice.

2.4.1 Using priority-setting exercises to define review questions

A research priority-setting exercise is a “collective activity for deciding which uncertainties are most worth trying to resolve through research; uncertainties considered may be problems to be understood or solutions to be developed or tested; across broad or narrow areas” (Sandy Oliver, referenced in Nasser 2018). Using research priority-setting exercises to define the scope of a review helps to prevent the waste of scarce resources for research by making the review more relevant to stakeholders (Chalmers et al 2014).

Research priority setting is always conducted in a specific context, setting and population with specific principles, values and preferences (which should be articulated). Different stakeholders’ interpretation of the scope and purpose of a ‘research question’ might vary, resulting in priorities that might be difficult to interpret. Researchers or review teams might find it necessary to translate the research priorities into an answerable PICO research question format, and may find it useful to recheck the question with the stakeholder groups to determine whether they have accurately reflected their intentions.

While Cochrane Review teams are in most cases reviewing the effects of an intervention with a global scope, they may find that the priorities identified by important stakeholders (such as the World Health Organization or other organizations or individuals in a representative health system) are informative in planning the review. Review authors may find that differences between different stakeholder groups’ views on priorities and the reasons for these differences can help them to define the scope of the review. This is particularly important for making decisions about excluding specific populations or settings, or being inclusive and potentially conducting subgroup analyses.

Whenever feasible, systematic reviews should be based on priorities identified by key stakeholders such as decision makers, patients/public, and practitioners. Cochrane has developed a list of priorities for reviews in consultation with key stakeholders, which is available on the Cochrane website. Issues relating to equity (see Chapter 16 and Section 2.4.3 ) need to be taken into account when conducting and interpreting the results from priority-setting exercises. Examples of materials to support these processes are available (Viergever et al 2010, Nasser et al 2013, Tong et al 2017).

The results of research priority-setting exercises can be searched for in electronic databases and via websites of relevant organizations. Examples are: James Lind Alliance , World Health Organization, organizations of health professionals including research disciplines, and ministries of health in different countries (Viergever 2010). Examples of search strategies for identifying research priority-setting exercises are available (Bryant et al 2014, Tong et al 2015).

Other sources of questions are often found in ‘implications for future research’ sections of articles in journals and clinical practice guidelines. Some guideline developers have prioritized questions identified through the guideline development process (Sharma et al 2018), although these priorities will be influenced by the needs of health systems in which different guideline development teams are working.

2.4.2 Engaging stakeholders to help define the review questions

In the absence of a relevant research priority-setting exercise, or when a systematic review is being conducted for a very specific purpose (for example, commissioned to inform the development of a guideline), researchers should work with relevant stakeholders to define the review question. This practice is especially important when developing review questions for studying the effectiveness of health systems and policies, because of the variability between countries and regions; the significance of these differences may only become apparent through discussion with the stakeholders.

The stakeholders for a review could include consumers or patients, carers, health professionals of different kinds, policy decision makers and others ( Chapter 1, Section 1.3.1 ). Identifying the stakeholders who are critical to a particular question will depend on the question, who the answer is likely to affect, and who will be expected to implement the intervention if it is found to be effective (or to discontinue it if not).

Stakeholder engagement should, optimally, be an ongoing process throughout the life of the systematic review, from defining the question to dissemination of results (Keown et al 2008). Engaging stakeholders increases relevance, promotes mutual learning, improves uptake and decreases research waste (see Chapter 1, Section 1.3.1 and Section 1.3.2 ). However, because such engagement can be challenging and resource intensive, a one-off engagement process to define the review question might only be possible. Review questions that are conceptualized and refined by multiple stakeholders can capture much of the complexity that should be addressed in a systematic review.

2.4.3 Considering issues relating to equity when defining review questions

Deciding what should be investigated, who the participants should be, and how the analysis will be carried out can be considered political activities, with the potential for increasing or decreasing inequalities in health. For example, we now know that well-intended interventions can actually widen inequalities in health outcomes since researchers have chosen to investigate this issue (Lorenc et al 2013). Decision makers can now take account of this knowledge when planning service provision. Authors should therefore consider the potential impact on disadvantaged groups of the intervention(s) that they are investigating on disadvantaged groups, and whether socio-economic inequalities in health might be affected depending on whether or how they are implemented.

Health equity is the absence of avoidable and unfair differences in health (Whitehead 1992). Health inequity may be experienced across characteristics defined by PROGRESS-Plus (Place of residence, Race/ethnicity/culture/language, Occupation, Gender/sex, Religion, Education, Socio-economic status, Social capital, and other characteristics (‘Plus’) such as sexual orientation, age, and disability) (O’Neill et al 2014). Issues relating to health equity should be considered when review questions are developed ( MECIR Box 2.4.a ). Chapter 16 presents detailed guidance on this issue for review authors.

MECIR Box 2.4 . a Relevant expectations for conduct of intervention reviews

2.5 Methods and tools for structuring the review

It is important for authors to develop the scope of their review with care: without a clear understanding of where the review will contribute to existing knowledge – and how it will be used – it may be at risk of conceptual incoherence. It may mis-specify critical elements of how the intervention(s) interact with the context(s) within which they operate to produce specific outcomes, and become either irrelevant or possibly misleading. For example, in a systematic review about smoking cessation interventions in pregnancy, it was essential for authors to take account of the way that health service provision has changed over time. The type and intensity of ‘usual care’ in more recent evaluations was equivalent to the interventions being evaluated in older studies, and the analysis needed to take this into account. This review also found that the same intervention can have different effects in different settings depending on whether its materials are culturally appropriate in each context (Chamberlain et al 2017).

In order to protect the review against conceptual incoherence and irrelevance, review authors need to spend time at the outset developing definitions for key concepts and ensuring that they are clear about the prior assumptions on which the review depends. These prior assumptions include, for example, why particular populations should be considered inside or outside the review’s scope; how the intervention is thought to achieve its effect; and why specific outcomes are selected for evaluation. Being clear about these prior assumptions also requires review authors to consider the evidential basis for these assumptions and decide for themselves which they can place more or less reliance on. When considered as a whole, this initial conceptual and definitional work states the review’s conceptual framework . Each element of the review’s PICO raises its own definitional challenges, which are discussed in detail in the Chapter 3 .

In this section we consider tools that may help to define the scope of the review and the relationships between its key concepts; in particular, articulating how the intervention gives rise to the outcomes selected. In some situations, long sequences of events are expected to occur between an intervention being implemented and an outcome being observed. For example, a systematic review examining the effects of asthma education interventions in schools on children’s health and well-being needed to consider: the interplay between core intervention components and their introduction into differing school environments; different child-level effect modifiers; how the intervention then had an impact on the knowledge of the child (and their family); the child’s self-efficacy and adherence to their treatment regime; the severity of their asthma; the number of days of restricted activity; how this affected their attendance at school; and finally, the distal outcomes of education attainment and indicators of child health and well-being (Kneale et al 2015).

Several specific tools can help authors to consider issues raised when defining review questions and planning their review; these are also helpful when developing eligibility criteria and classifying included studies. These include the following.

• Taxonomies: hierarchical structures that can be used to categorize (or group) related interventions, outcomes or populations.
• Generic frameworks for examining and structuring the description of intervention characteristics (e.g. TIDieR for the description of interventions (Hoffmann et al 2014), iCAT_SR for describing multiple aspects of complexity in systematic reviews (Lewin et al 2017)).
• Core outcome sets for identifying and defining agreed outcomes that should be measured for specific health conditions (described in more detail in Chapter 3 ).

Unlike these tools, which focus on particular aspects of a review, logic models provide a framework for planning and guiding synthesis at the review level (see Section 2.5.1 ).

2.5.1 Logic models

Logic models (sometimes referred to as conceptual frameworks or theories of change) are graphical representations of theories about how interventions work. They depict intervention components, mechanisms (pathways of action), outputs, and outcomes as sequential (although not necessarily linear) chains of events. Among systematic review authors, they were originally proposed as a useful tool when working with evaluations of complex social and population health programmes and interventions, to conceptualize the pathways through which interventions are intended to change outcomes (Anderson et al 2011).

In reviews where intervention complexity is a key consideration (see Chapter 17 ), logic models can be particularly helpful. For example, in a review of psychosocial group interventions for those with HIV, a logic model was used to show how the intervention might work (van der Heijden et al 2017). The review authors depicted proximal outcomes, such as self-esteem, but chose only to include psychological health outcomes in their review. In contrast, Bailey and colleagues included proximal outcomes in their review of computer-based interventions for sexual health promotion using a logic model to show how outcomes were grouped (Bailey et al 2010). Finally, in a review of slum upgrading, a logic model showed the broad range of interventions and their interlinkages with health and socio-economic outcomes (Turley et al 2013), and enabled the review authors to select a specific intervention category (physical upgrading) on which to focus the review. Further resources provide further examples of logic models, and can help review authors develop and use logic models (Anderson et al 2011, Baxter et al 2014, Kneale et al 2015, Pfadenhauer et al 2017, Rohwer et al 2017).

Logic models can vary in their emphasis, with a distinction sometimes made between system-based and process-oriented logic models (Rehfuess et al 2018). System-based logic models have particular value in examining the complexity of the system (e.g. the geographical, epidemiological, political, socio-cultural and socio-economic features of a system), and the interactions between contextual features, participants and the intervention (see Chapter 17 ). Process-oriented logic models aim to capture the complexity of causal pathways by which the intervention leads to outcomes, and any factors that may modify intervention effects. However, this is not a crisp distinction; the two types are interrelated; with some logic models depicting elements of both systems and process models simultaneously.

The way that logic models can be represented diagrammatically (see Chapter 17 for an example) provides a valuable visual summary for readers and can be a communication tool for decision makers and practitioners. They can aid initially in the development of a shared understanding between different stakeholders of the scope of the review and its PICO, helping to support decisions taken throughout the review process, from developing the research question and setting the review parameters, to structuring and interpreting the results. They can be used in planning the PICO elements of a review as well as for determining how the synthesis will be structured (i.e. planned comparisons, including intervention and comparator groups, and any grouping of outcome and population subgroups). These models may help review authors specify the link between the intervention, proximal and distal outcomes, and mediating factors. In other words, they depict the intervention theory underpinning the synthesis plan.

Anderson and colleagues note the main value of logic models in systematic review as (Anderson et al 2011):

• refining review questions;
• deciding on ‘lumping’ or ‘splitting’ a review topic;
• identifying intervention components;
• defining and conducting the review;
• identifying relevant study eligibility criteria;
• guiding the literature search strategy;
• explaining the rationale behind surrogate outcomes used in the review;
• justifying the need for subgroup analyses (e.g. age, sex/gender, socio-economic status);
• making the review relevant to policy and practice;
• structuring the reporting of results;
• illustrating how harms and feasibility are connected with interventions; and
• interpreting results based on intervention theory and systems thinking (see Chapter 17 ).

Logic models can be useful in systematic reviews when considering whether failure to find a beneficial effect of an intervention is due to a theory failure, an implementation failure, or both (see Chapter 17 and Cargo et al 2018). Making a distinction between implementation and intervention theory can help to determine whether and how the intervention interacts with (and potentially changes) its context (see Chapter 3 and Chapter 17 for further discussion of context). This helps to elucidate situations in which variations in how the intervention is implemented have the potential to affect the integrity of the intervention and intended outcomes.

Given their potential value in conceptualizing and structuring a review, logic models are increasingly published in review protocols. Logic models may be specified a priori and remain unchanged throughout the review; it might be expected, however, that the findings of reviews produce evidence and new understandings that could be used to update the logic model in some way (Kneale et al 2015). Some reviews take a more staged approach, pre-specifying points in the review process where the model may be revised on the basis of (new) evidence (Rehfuess et al 2018) and a staged logic model can provide an efficient way to report revisions to the synthesis plan. For example, in a review of portion, package and tableware size for changing selection or consumption of food and other products, the authors presented a logic model that clearly showed changes to their original synthesis plan (Hollands et al 2015).

It is preferable to seek out existing logic models for the intervention and revise or adapt these models in line with the review focus, although this may not always be possible. More commonly, new models are developed starting with the identification of outcomes and theorizing the necessary pre-conditions to reach those outcomes. This process of theorizing and identifying the steps and necessary pre-conditions continues, working backwards from the intended outcomes, until the intervention itself is represented. As many mechanisms of action are invisible and can only be ‘known’ through theory, this process is invaluable in exposing assumptions as to how interventions are thought to work; assumptions that might then be tested in the review. Logic models can be developed with stakeholders (see Section 2.5.2 ) and it is considered good practice to obtain stakeholder input in their development.

Logic models are representations of how interventions are intended to ‘work’, but they can also provide a useful basis for thinking through the unintended consequences of interventions and identifying potential adverse effects that may need to be captured in the review (Bonell et al 2015). While logic models provide a guiding theory of how interventions are intended to work, critiques exist around their use, including their potential to oversimplify complex intervention processes (Rohwer et al 2017). Here, contributions from different stakeholders to the development of a logic model may be able to articulate where complex processes may occur; theorizing unintended intervention impacts; and the explicit representation of ambiguity within certain parts of the causal chain where new theory/explanation is most valuable.

2.5.2 Changing review questions

While questions should be posed in the protocol before initiating the full review, these questions should not prevent exploration of unexpected issues. Reviews are analyses of existing data that are constrained by previously chosen study populations, settings, intervention formulations, outcome measures and study designs. It is generally not possible to formulate an answerable question for a review without knowing some of the studies relevant to the question, and it may become clear that the questions a review addresses need to be modified in light of evidence accumulated in the process of conducting the review.

Although a certain fluidity and refinement of questions is to be expected in reviews as a fuller understanding of the evidence is gained, it is important to guard against bias in modifying questions. Data-driven questions can generate false conclusions based on spurious results. Any changes to the protocol that result from revising the question for the review should be documented at the beginning of the Methods section. Sensitivity analyses may be used to assess the impact of changes on the review findings (see Chapter 10, Section 10.14 ). When refining questions it is useful to ask the following questions.

• What is the motivation for the refinement?
• Could the refinement have been influenced by results from any of the included studies?
• Does the refined question require a modification to the search strategy and/or reassessment of any decisions regarding study eligibility?
• Are data collection methods appropriate to the refined question?
• Does the refined question still meet the FINER criteria discussed in Section 2.1 ?

2.5.3 Building in contingencies to deal with sparse data

The ability to address the review questions will depend on the maturity and validity of the evidence base. When few studies are identified, there will be limited opportunity to address the question through an informative synthesis. In anticipation of this scenario, review authors may build contingencies into their protocol analysis plan that specify grouping (any or multiple) PICO elements at a broader level; thus potentially enabling synthesis of a larger number of studies. Broader groupings will generally address a less specific question, for example:

• ‘the effect of any antioxidant supplement on …’ instead of ‘the effect of vitamin C on …’;
• ‘the effect of sexual health promotion on biological outcomes ’ instead of ‘the effect of sexual health promotion on sexually transmitted infections ’; or
• ‘the effect of cognitive behavioural therapy in children and adolescents on …’ instead of ‘the effect of cognitive behavioural therapy in children on …’.

However, such broader questions may be useful for identifying important leads in areas that lack effective interventions and for guiding future research. Changes in the grouping may affect the assessment of the certainty of the evidence (see Chapter 14 ).

2.5.4 Economic data

Decision makers need to consider the economic aspects of an intervention, such as whether its adoption will lead to a more efficient use of resources. Economic data such as resource use, costs or cost-effectiveness (or a combination of these) may therefore be included as outcomes in a review. It is useful to break down measures of resource use and costs to the level of specific items or categories. It is helpful to consider an international perspective in the discussion of costs. Economics issues are discussed in detail in Chapter 20 .

2.6 Chapter information

Authors: James Thomas, Dylan Kneale, Joanne E McKenzie, Sue E Brennan, Soumyadeep Bhaumik

Acknowledgements: This chapter builds on earlier versions of the Handbook . Mona Nasser, Dan Fox and Sally Crowe contributed to Section 2.4 ; Hilary J Thomson contributed to Section 2.5.1 .

Funding: JT and DK are supported by the National Institute for Health Research (NIHR) Collaboration for Leadership in Applied Health Research and Care North Thames at Barts Health NHS Trust. JEM is supported by an Australian National Health and Medical Research Council (NHMRC) Career Development Fellowship (1143429). SEB’s position is supported by the NHMRC Cochrane Collaboration Funding Program. The views expressed are those of the authors and not necessarily those of the NHS, the NIHR, the Department of Health or the NHMRC.

2.7 References

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What is a Literature Review? How to Write It (with Examples)

A literature review is a critical analysis and synthesis of existing research on a particular topic. It provides an overview of the current state of knowledge, identifies gaps, and highlights key findings in the literature. 1 The purpose of a literature review is to situate your own research within the context of existing scholarship, demonstrating your understanding of the topic and showing how your work contributes to the ongoing conversation in the field. Learning how to write a literature review is a critical tool for successful research. Your ability to summarize and synthesize prior research pertaining to a certain topic demonstrates your grasp on the topic of study, and assists in the learning process. 

Table of Contents

• What is the purpose of literature review? 
• a. Habitat Loss and Species Extinction: 
• b. Range Shifts and Phenological Changes: 
• c. Ocean Acidification and Coral Reefs: 
• d. Adaptive Strategies and Conservation Efforts: 
• How to write a good literature review 
• Choose a Topic and Define the Research Question: 
• Decide on the Scope of Your Review: 
• Select Databases for Searches: 
• Conduct Searches and Keep Track: 
• Review the Literature: 
• Organize and Write Your Literature Review: 
• Frequently asked questions 

What is a literature review?

A well-conducted literature review demonstrates the researcher’s familiarity with the existing literature, establishes the context for their own research, and contributes to scholarly conversations on the topic. One of the purposes of a literature review is also to help researchers avoid duplicating previous work and ensure that their research is informed by and builds upon the existing body of knowledge.

What is the purpose of literature review?

A literature review serves several important purposes within academic and research contexts. Here are some key objectives and functions of a literature review: 2  

• Contextualizing the Research Problem: The literature review provides a background and context for the research problem under investigation. It helps to situate the study within the existing body of knowledge. 
• Identifying Gaps in Knowledge: By identifying gaps, contradictions, or areas requiring further research, the researcher can shape the research question and justify the significance of the study. This is crucial for ensuring that the new research contributes something novel to the field. 
• Understanding Theoretical and Conceptual Frameworks: Literature reviews help researchers gain an understanding of the theoretical and conceptual frameworks used in previous studies. This aids in the development of a theoretical framework for the current research. 
• Providing Methodological Insights: Another purpose of literature reviews is that it allows researchers to learn about the methodologies employed in previous studies. This can help in choosing appropriate research methods for the current study and avoiding pitfalls that others may have encountered. 
• Establishing Credibility: A well-conducted literature review demonstrates the researcher’s familiarity with existing scholarship, establishing their credibility and expertise in the field. It also helps in building a solid foundation for the new research. 
• Informing Hypotheses or Research Questions: The literature review guides the formulation of hypotheses or research questions by highlighting relevant findings and areas of uncertainty in existing literature. 

Literature review example

Let’s delve deeper with a literature review example: Let’s say your literature review is about the impact of climate change on biodiversity. You might format your literature review into sections such as the effects of climate change on habitat loss and species extinction, phenological changes, and marine biodiversity. Each section would then summarize and analyze relevant studies in those areas, highlighting key findings and identifying gaps in the research. The review would conclude by emphasizing the need for further research on specific aspects of the relationship between climate change and biodiversity. The following literature review template provides a glimpse into the recommended literature review structure and content, demonstrating how research findings are organized around specific themes within a broader topic. 

Literature Review on Climate Change Impacts on Biodiversity:

Climate change is a global phenomenon with far-reaching consequences, including significant impacts on biodiversity. This literature review synthesizes key findings from various studies: 

a. Habitat Loss and Species Extinction:

Climate change-induced alterations in temperature and precipitation patterns contribute to habitat loss, affecting numerous species (Thomas et al., 2004). The review discusses how these changes increase the risk of extinction, particularly for species with specific habitat requirements. 

b. Range Shifts and Phenological Changes:

Observations of range shifts and changes in the timing of biological events (phenology) are documented in response to changing climatic conditions (Parmesan & Yohe, 2003). These shifts affect ecosystems and may lead to mismatches between species and their resources. 

c. Ocean Acidification and Coral Reefs:

The review explores the impact of climate change on marine biodiversity, emphasizing ocean acidification’s threat to coral reefs (Hoegh-Guldberg et al., 2007). Changes in pH levels negatively affect coral calcification, disrupting the delicate balance of marine ecosystems. 

d. Adaptive Strategies and Conservation Efforts:

Recognizing the urgency of the situation, the literature review discusses various adaptive strategies adopted by species and conservation efforts aimed at mitigating the impacts of climate change on biodiversity (Hannah et al., 2007). It emphasizes the importance of interdisciplinary approaches for effective conservation planning. 

How to write a good literature review

Writing a literature review involves summarizing and synthesizing existing research on a particular topic. A good literature review format should include the following elements. 

Introduction: The introduction sets the stage for your literature review, providing context and introducing the main focus of your review. 

• Opening Statement: Begin with a general statement about the broader topic and its significance in the field. 
• Scope and Purpose: Clearly define the scope of your literature review. Explain the specific research question or objective you aim to address. 
• Organizational Framework: Briefly outline the structure of your literature review, indicating how you will categorize and discuss the existing research. 
• Significance of the Study: Highlight why your literature review is important and how it contributes to the understanding of the chosen topic. 
• Thesis Statement: Conclude the introduction with a concise thesis statement that outlines the main argument or perspective you will develop in the body of the literature review. 

Body: The body of the literature review is where you provide a comprehensive analysis of existing literature, grouping studies based on themes, methodologies, or other relevant criteria. 

• Organize by Theme or Concept: Group studies that share common themes, concepts, or methodologies. Discuss each theme or concept in detail, summarizing key findings and identifying gaps or areas of disagreement. 
• Critical Analysis: Evaluate the strengths and weaknesses of each study. Discuss the methodologies used, the quality of evidence, and the overall contribution of each work to the understanding of the topic. 
• Synthesis of Findings: Synthesize the information from different studies to highlight trends, patterns, or areas of consensus in the literature. 
• Identification of Gaps: Discuss any gaps or limitations in the existing research and explain how your review contributes to filling these gaps. 
• Transition between Sections: Provide smooth transitions between different themes or concepts to maintain the flow of your literature review. 

Conclusion: The conclusion of your literature review should summarize the main findings, highlight the contributions of the review, and suggest avenues for future research. 

• Summary of Key Findings: Recap the main findings from the literature and restate how they contribute to your research question or objective. 
• Contributions to the Field: Discuss the overall contribution of your literature review to the existing knowledge in the field. 
• Implications and Applications: Explore the practical implications of the findings and suggest how they might impact future research or practice. 
• Recommendations for Future Research: Identify areas that require further investigation and propose potential directions for future research in the field. 
• Final Thoughts: Conclude with a final reflection on the importance of your literature review and its relevance to the broader academic community. 

Conducting a literature review

Conducting a literature review is an essential step in research that involves reviewing and analyzing existing literature on a specific topic. It’s important to know how to do a literature review effectively, so here are the steps to follow: 1  

Choose a Topic and Define the Research Question:

• Select a topic that is relevant to your field of study. 
• Clearly define your research question or objective. Determine what specific aspect of the topic do you want to explore? 

Decide on the Scope of Your Review:

• Determine the timeframe for your literature review. Are you focusing on recent developments, or do you want a historical overview? 
• Consider the geographical scope. Is your review global, or are you focusing on a specific region? 
• Define the inclusion and exclusion criteria. What types of sources will you include? Are there specific types of studies or publications you will exclude? 

Select Databases for Searches:

• Identify relevant databases for your field. Examples include PubMed, IEEE Xplore, Scopus, Web of Science, and Google Scholar. 
• Consider searching in library catalogs, institutional repositories, and specialized databases related to your topic. 

Conduct Searches and Keep Track:

• Develop a systematic search strategy using keywords, Boolean operators (AND, OR, NOT), and other search techniques. 
• Record and document your search strategy for transparency and replicability. 
• Keep track of the articles, including publication details, abstracts, and links. Use citation management tools like EndNote, Zotero, or Mendeley to organize your references. 

Review the Literature:

• Evaluate the relevance and quality of each source. Consider the methodology, sample size, and results of studies. 
• Organize the literature by themes or key concepts. Identify patterns, trends, and gaps in the existing research. 
• Summarize key findings and arguments from each source. Compare and contrast different perspectives. 
• Identify areas where there is a consensus in the literature and where there are conflicting opinions. 
• Provide critical analysis and synthesis of the literature. What are the strengths and weaknesses of existing research? 

Organize and Write Your Literature Review:

• Literature review outline should be based on themes, chronological order, or methodological approaches. 
• Write a clear and coherent narrative that synthesizes the information gathered. 
• Use proper citations for each source and ensure consistency in your citation style (APA, MLA, Chicago, etc.). 
• Conclude your literature review by summarizing key findings, identifying gaps, and suggesting areas for future research. 

The literature review sample and detailed advice on writing and conducting a review will help you produce a well-structured report. But remember that a literature review is an ongoing process, and it may be necessary to revisit and update it as your research progresses. 

Frequently asked questions

A literature review is a critical and comprehensive analysis of existing literature (published and unpublished works) on a specific topic or research question and provides a synthesis of the current state of knowledge in a particular field. A well-conducted literature review is crucial for researchers to build upon existing knowledge, avoid duplication of efforts, and contribute to the advancement of their field. It also helps researchers situate their work within a broader context and facilitates the development of a sound theoretical and conceptual framework for their studies.

Literature review is a crucial component of research writing, providing a solid background for a research paper’s investigation. The aim is to keep professionals up to date by providing an understanding of ongoing developments within a specific field, including research methods, and experimental techniques used in that field, and present that knowledge in the form of a written report. Also, the depth and breadth of the literature review emphasizes the credibility of the scholar in his or her field.  

Before writing a literature review, it’s essential to undertake several preparatory steps to ensure that your review is well-researched, organized, and focused. This includes choosing a topic of general interest to you and doing exploratory research on that topic, writing an annotated bibliography, and noting major points, especially those that relate to the position you have taken on the topic. 

Literature reviews and academic research papers are essential components of scholarly work but serve different purposes within the academic realm. 3 A literature review aims to provide a foundation for understanding the current state of research on a particular topic, identify gaps or controversies, and lay the groundwork for future research. Therefore, it draws heavily from existing academic sources, including books, journal articles, and other scholarly publications. In contrast, an academic research paper aims to present new knowledge, contribute to the academic discourse, and advance the understanding of a specific research question. Therefore, it involves a mix of existing literature (in the introduction and literature review sections) and original data or findings obtained through research methods. 

Literature reviews are essential components of academic and research papers, and various strategies can be employed to conduct them effectively. If you want to know how to write a literature review for a research paper, here are four common approaches that are often used by researchers.  Chronological Review: This strategy involves organizing the literature based on the chronological order of publication. It helps to trace the development of a topic over time, showing how ideas, theories, and research have evolved.  Thematic Review: Thematic reviews focus on identifying and analyzing themes or topics that cut across different studies. Instead of organizing the literature chronologically, it is grouped by key themes or concepts, allowing for a comprehensive exploration of various aspects of the topic.  Methodological Review: This strategy involves organizing the literature based on the research methods employed in different studies. It helps to highlight the strengths and weaknesses of various methodologies and allows the reader to evaluate the reliability and validity of the research findings.  Theoretical Review: A theoretical review examines the literature based on the theoretical frameworks used in different studies. This approach helps to identify the key theories that have been applied to the topic and assess their contributions to the understanding of the subject.  It’s important to note that these strategies are not mutually exclusive, and a literature review may combine elements of more than one approach. The choice of strategy depends on the research question, the nature of the literature available, and the goals of the review. Additionally, other strategies, such as integrative reviews or systematic reviews, may be employed depending on the specific requirements of the research.

The literature review format can vary depending on the specific publication guidelines. However, there are some common elements and structures that are often followed. Here is a general guideline for the format of a literature review:  Introduction:   Provide an overview of the topic.  Define the scope and purpose of the literature review.  State the research question or objective.  Body:   Organize the literature by themes, concepts, or chronology.  Critically analyze and evaluate each source.  Discuss the strengths and weaknesses of the studies.  Highlight any methodological limitations or biases.  Identify patterns, connections, or contradictions in the existing research.  Conclusion:   Summarize the key points discussed in the literature review.  Highlight the research gap.  Address the research question or objective stated in the introduction.  Highlight the contributions of the review and suggest directions for future research.

Both annotated bibliographies and literature reviews involve the examination of scholarly sources. While annotated bibliographies focus on individual sources with brief annotations, literature reviews provide a more in-depth, integrated, and comprehensive analysis of existing literature on a specific topic. The key differences are as follows: 

References 

• Denney, A. S., & Tewksbury, R. (2013). How to write a literature review.  Journal of criminal justice education ,  24 (2), 218-234. 
• Pan, M. L. (2016).  Preparing literature reviews: Qualitative and quantitative approaches . Taylor & Francis. 
• Cantero, C. (2019). How to write a literature review.  San José State University Writing Center . 

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Lau F, Kuziemsky C, editors. Handbook of eHealth Evaluation: An Evidence-based Approach [Internet]. Victoria (BC): University of Victoria; 2017 Feb 27.

Handbook of eHealth Evaluation: An Evidence-based Approach [Internet].

Chapter 9 methods for literature reviews.

Guy Paré and Spyros Kitsiou .

9.1. Introduction

Literature reviews play a critical role in scholarship because science remains, first and foremost, a cumulative endeavour ( vom Brocke et al., 2009 ). As in any academic discipline, rigorous knowledge syntheses are becoming indispensable in keeping up with an exponentially growing eHealth literature, assisting practitioners, academics, and graduate students in finding, evaluating, and synthesizing the contents of many empirical and conceptual papers. Among other methods, literature reviews are essential for: (a) identifying what has been written on a subject or topic; (b) determining the extent to which a specific research area reveals any interpretable trends or patterns; (c) aggregating empirical findings related to a narrow research question to support evidence-based practice; (d) generating new frameworks and theories; and (e) identifying topics or questions requiring more investigation ( Paré, Trudel, Jaana, & Kitsiou, 2015 ).

Literature reviews can take two major forms. The most prevalent one is the “literature review” or “background” section within a journal paper or a chapter in a graduate thesis. This section synthesizes the extant literature and usually identifies the gaps in knowledge that the empirical study addresses ( Sylvester, Tate, & Johnstone, 2013 ). It may also provide a theoretical foundation for the proposed study, substantiate the presence of the research problem, justify the research as one that contributes something new to the cumulated knowledge, or validate the methods and approaches for the proposed study ( Hart, 1998 ; Levy & Ellis, 2006 ).

The second form of literature review, which is the focus of this chapter, constitutes an original and valuable work of research in and of itself ( Paré et al., 2015 ). Rather than providing a base for a researcher’s own work, it creates a solid starting point for all members of the community interested in a particular area or topic ( Mulrow, 1987 ). The so-called “review article” is a journal-length paper which has an overarching purpose to synthesize the literature in a field, without collecting or analyzing any primary data ( Green, Johnson, & Adams, 2006 ).

When appropriately conducted, review articles represent powerful information sources for practitioners looking for state-of-the art evidence to guide their decision-making and work practices ( Paré et al., 2015 ). Further, high-quality reviews become frequently cited pieces of work which researchers seek out as a first clear outline of the literature when undertaking empirical studies ( Cooper, 1988 ; Rowe, 2014 ). Scholars who track and gauge the impact of articles have found that review papers are cited and downloaded more often than any other type of published article ( Cronin, Ryan, & Coughlan, 2008 ; Montori, Wilczynski, Morgan, Haynes, & Hedges, 2003 ; Patsopoulos, Analatos, & Ioannidis, 2005 ). The reason for their popularity may be the fact that reading the review enables one to have an overview, if not a detailed knowledge of the area in question, as well as references to the most useful primary sources ( Cronin et al., 2008 ). Although they are not easy to conduct, the commitment to complete a review article provides a tremendous service to one’s academic community ( Paré et al., 2015 ; Petticrew & Roberts, 2006 ). Most, if not all, peer-reviewed journals in the fields of medical informatics publish review articles of some type.

The main objectives of this chapter are fourfold: (a) to provide an overview of the major steps and activities involved in conducting a stand-alone literature review; (b) to describe and contrast the different types of review articles that can contribute to the eHealth knowledge base; (c) to illustrate each review type with one or two examples from the eHealth literature; and (d) to provide a series of recommendations for prospective authors of review articles in this domain.

9.2. Overview of the Literature Review Process and Steps

As explained in Templier and Paré (2015) , there are six generic steps involved in conducting a review article:

• formulating the research question(s) and objective(s),
• searching the extant literature,
• screening for inclusion,
• assessing the quality of primary studies,
• extracting data, and
• analyzing data.

Although these steps are presented here in sequential order, one must keep in mind that the review process can be iterative and that many activities can be initiated during the planning stage and later refined during subsequent phases ( Finfgeld-Connett & Johnson, 2013 ; Kitchenham & Charters, 2007 ).

Formulating the research question(s) and objective(s): As a first step, members of the review team must appropriately justify the need for the review itself ( Petticrew & Roberts, 2006 ), identify the review’s main objective(s) ( Okoli & Schabram, 2010 ), and define the concepts or variables at the heart of their synthesis ( Cooper & Hedges, 2009 ; Webster & Watson, 2002 ). Importantly, they also need to articulate the research question(s) they propose to investigate ( Kitchenham & Charters, 2007 ). In this regard, we concur with Jesson, Matheson, and Lacey (2011) that clearly articulated research questions are key ingredients that guide the entire review methodology; they underscore the type of information that is needed, inform the search for and selection of relevant literature, and guide or orient the subsequent analysis. Searching the extant literature: The next step consists of searching the literature and making decisions about the suitability of material to be considered in the review ( Cooper, 1988 ). There exist three main coverage strategies. First, exhaustive coverage means an effort is made to be as comprehensive as possible in order to ensure that all relevant studies, published and unpublished, are included in the review and, thus, conclusions are based on this all-inclusive knowledge base. The second type of coverage consists of presenting materials that are representative of most other works in a given field or area. Often authors who adopt this strategy will search for relevant articles in a small number of top-tier journals in a field ( Paré et al., 2015 ). In the third strategy, the review team concentrates on prior works that have been central or pivotal to a particular topic. This may include empirical studies or conceptual papers that initiated a line of investigation, changed how problems or questions were framed, introduced new methods or concepts, or engendered important debate ( Cooper, 1988 ). Screening for inclusion: The following step consists of evaluating the applicability of the material identified in the preceding step ( Levy & Ellis, 2006 ; vom Brocke et al., 2009 ). Once a group of potential studies has been identified, members of the review team must screen them to determine their relevance ( Petticrew & Roberts, 2006 ). A set of predetermined rules provides a basis for including or excluding certain studies. This exercise requires a significant investment on the part of researchers, who must ensure enhanced objectivity and avoid biases or mistakes. As discussed later in this chapter, for certain types of reviews there must be at least two independent reviewers involved in the screening process and a procedure to resolve disagreements must also be in place ( Liberati et al., 2009 ; Shea et al., 2009 ). Assessing the quality of primary studies: In addition to screening material for inclusion, members of the review team may need to assess the scientific quality of the selected studies, that is, appraise the rigour of the research design and methods. Such formal assessment, which is usually conducted independently by at least two coders, helps members of the review team refine which studies to include in the final sample, determine whether or not the differences in quality may affect their conclusions, or guide how they analyze the data and interpret the findings ( Petticrew & Roberts, 2006 ). Ascribing quality scores to each primary study or considering through domain-based evaluations which study components have or have not been designed and executed appropriately makes it possible to reflect on the extent to which the selected study addresses possible biases and maximizes validity ( Shea et al., 2009 ). Extracting data: The following step involves gathering or extracting applicable information from each primary study included in the sample and deciding what is relevant to the problem of interest ( Cooper & Hedges, 2009 ). Indeed, the type of data that should be recorded mainly depends on the initial research questions ( Okoli & Schabram, 2010 ). However, important information may also be gathered about how, when, where and by whom the primary study was conducted, the research design and methods, or qualitative/quantitative results ( Cooper & Hedges, 2009 ). Analyzing and synthesizing data : As a final step, members of the review team must collate, summarize, aggregate, organize, and compare the evidence extracted from the included studies. The extracted data must be presented in a meaningful way that suggests a new contribution to the extant literature ( Jesson et al., 2011 ). Webster and Watson (2002) warn researchers that literature reviews should be much more than lists of papers and should provide a coherent lens to make sense of extant knowledge on a given topic. There exist several methods and techniques for synthesizing quantitative (e.g., frequency analysis, meta-analysis) and qualitative (e.g., grounded theory, narrative analysis, meta-ethnography) evidence ( Dixon-Woods, Agarwal, Jones, Young, & Sutton, 2005 ; Thomas & Harden, 2008 ).

9.3. Types of Review Articles and Brief Illustrations

EHealth researchers have at their disposal a number of approaches and methods for making sense out of existing literature, all with the purpose of casting current research findings into historical contexts or explaining contradictions that might exist among a set of primary research studies conducted on a particular topic. Our classification scheme is largely inspired from Paré and colleagues’ (2015) typology. Below we present and illustrate those review types that we feel are central to the growth and development of the eHealth domain.

9.3.1. Narrative Reviews

The narrative review is the “traditional” way of reviewing the extant literature and is skewed towards a qualitative interpretation of prior knowledge ( Sylvester et al., 2013 ). Put simply, a narrative review attempts to summarize or synthesize what has been written on a particular topic but does not seek generalization or cumulative knowledge from what is reviewed ( Davies, 2000 ; Green et al., 2006 ). Instead, the review team often undertakes the task of accumulating and synthesizing the literature to demonstrate the value of a particular point of view ( Baumeister & Leary, 1997 ). As such, reviewers may selectively ignore or limit the attention paid to certain studies in order to make a point. In this rather unsystematic approach, the selection of information from primary articles is subjective, lacks explicit criteria for inclusion and can lead to biased interpretations or inferences ( Green et al., 2006 ). There are several narrative reviews in the particular eHealth domain, as in all fields, which follow such an unstructured approach ( Silva et al., 2015 ; Paul et al., 2015 ).

Despite these criticisms, this type of review can be very useful in gathering together a volume of literature in a specific subject area and synthesizing it. As mentioned above, its primary purpose is to provide the reader with a comprehensive background for understanding current knowledge and highlighting the significance of new research ( Cronin et al., 2008 ). Faculty like to use narrative reviews in the classroom because they are often more up to date than textbooks, provide a single source for students to reference, and expose students to peer-reviewed literature ( Green et al., 2006 ). For researchers, narrative reviews can inspire research ideas by identifying gaps or inconsistencies in a body of knowledge, thus helping researchers to determine research questions or formulate hypotheses. Importantly, narrative reviews can also be used as educational articles to bring practitioners up to date with certain topics of issues ( Green et al., 2006 ).

Recently, there have been several efforts to introduce more rigour in narrative reviews that will elucidate common pitfalls and bring changes into their publication standards. Information systems researchers, among others, have contributed to advancing knowledge on how to structure a “traditional” review. For instance, Levy and Ellis (2006) proposed a generic framework for conducting such reviews. Their model follows the systematic data processing approach comprised of three steps, namely: (a) literature search and screening; (b) data extraction and analysis; and (c) writing the literature review. They provide detailed and very helpful instructions on how to conduct each step of the review process. As another methodological contribution, vom Brocke et al. (2009) offered a series of guidelines for conducting literature reviews, with a particular focus on how to search and extract the relevant body of knowledge. Last, Bandara, Miskon, and Fielt (2011) proposed a structured, predefined and tool-supported method to identify primary studies within a feasible scope, extract relevant content from identified articles, synthesize and analyze the findings, and effectively write and present the results of the literature review. We highly recommend that prospective authors of narrative reviews consult these useful sources before embarking on their work.

Darlow and Wen (2015) provide a good example of a highly structured narrative review in the eHealth field. These authors synthesized published articles that describe the development process of mobile health ( m-health ) interventions for patients’ cancer care self-management. As in most narrative reviews, the scope of the research questions being investigated is broad: (a) how development of these systems are carried out; (b) which methods are used to investigate these systems; and (c) what conclusions can be drawn as a result of the development of these systems. To provide clear answers to these questions, a literature search was conducted on six electronic databases and Google Scholar . The search was performed using several terms and free text words, combining them in an appropriate manner. Four inclusion and three exclusion criteria were utilized during the screening process. Both authors independently reviewed each of the identified articles to determine eligibility and extract study information. A flow diagram shows the number of studies identified, screened, and included or excluded at each stage of study selection. In terms of contributions, this review provides a series of practical recommendations for m-health intervention development.

9.3.2. Descriptive or Mapping Reviews

The primary goal of a descriptive review is to determine the extent to which a body of knowledge in a particular research topic reveals any interpretable pattern or trend with respect to pre-existing propositions, theories, methodologies or findings ( King & He, 2005 ; Paré et al., 2015 ). In contrast with narrative reviews, descriptive reviews follow a systematic and transparent procedure, including searching, screening and classifying studies ( Petersen, Vakkalanka, & Kuzniarz, 2015 ). Indeed, structured search methods are used to form a representative sample of a larger group of published works ( Paré et al., 2015 ). Further, authors of descriptive reviews extract from each study certain characteristics of interest, such as publication year, research methods, data collection techniques, and direction or strength of research outcomes (e.g., positive, negative, or non-significant) in the form of frequency analysis to produce quantitative results ( Sylvester et al., 2013 ). In essence, each study included in a descriptive review is treated as the unit of analysis and the published literature as a whole provides a database from which the authors attempt to identify any interpretable trends or draw overall conclusions about the merits of existing conceptualizations, propositions, methods or findings ( Paré et al., 2015 ). In doing so, a descriptive review may claim that its findings represent the state of the art in a particular domain ( King & He, 2005 ).

In the fields of health sciences and medical informatics, reviews that focus on examining the range, nature and evolution of a topic area are described by Anderson, Allen, Peckham, and Goodwin (2008) as mapping reviews . Like descriptive reviews, the research questions are generic and usually relate to publication patterns and trends. There is no preconceived plan to systematically review all of the literature although this can be done. Instead, researchers often present studies that are representative of most works published in a particular area and they consider a specific time frame to be mapped.

An example of this approach in the eHealth domain is offered by DeShazo, Lavallie, and Wolf (2009). The purpose of this descriptive or mapping review was to characterize publication trends in the medical informatics literature over a 20-year period (1987 to 2006). To achieve this ambitious objective, the authors performed a bibliometric analysis of medical informatics citations indexed in medline using publication trends, journal frequencies, impact factors, Medical Subject Headings (MeSH) term frequencies, and characteristics of citations. Findings revealed that there were over 77,000 medical informatics articles published during the covered period in numerous journals and that the average annual growth rate was 12%. The MeSH term analysis also suggested a strong interdisciplinary trend. Finally, average impact scores increased over time with two notable growth periods. Overall, patterns in research outputs that seem to characterize the historic trends and current components of the field of medical informatics suggest it may be a maturing discipline (DeShazo et al., 2009).

9.3.3. Scoping Reviews

Scoping reviews attempt to provide an initial indication of the potential size and nature of the extant literature on an emergent topic (Arksey & O’Malley, 2005; Daudt, van Mossel, & Scott, 2013 ; Levac, Colquhoun, & O’Brien, 2010). A scoping review may be conducted to examine the extent, range and nature of research activities in a particular area, determine the value of undertaking a full systematic review (discussed next), or identify research gaps in the extant literature ( Paré et al., 2015 ). In line with their main objective, scoping reviews usually conclude with the presentation of a detailed research agenda for future works along with potential implications for both practice and research.

Unlike narrative and descriptive reviews, the whole point of scoping the field is to be as comprehensive as possible, including grey literature (Arksey & O’Malley, 2005). Inclusion and exclusion criteria must be established to help researchers eliminate studies that are not aligned with the research questions. It is also recommended that at least two independent coders review abstracts yielded from the search strategy and then the full articles for study selection ( Daudt et al., 2013 ). The synthesized evidence from content or thematic analysis is relatively easy to present in tabular form (Arksey & O’Malley, 2005; Thomas & Harden, 2008 ).

One of the most highly cited scoping reviews in the eHealth domain was published by Archer, Fevrier-Thomas, Lokker, McKibbon, and Straus (2011) . These authors reviewed the existing literature on personal health record ( phr ) systems including design, functionality, implementation, applications, outcomes, and benefits. Seven databases were searched from 1985 to March 2010. Several search terms relating to phr s were used during this process. Two authors independently screened titles and abstracts to determine inclusion status. A second screen of full-text articles, again by two independent members of the research team, ensured that the studies described phr s. All in all, 130 articles met the criteria and their data were extracted manually into a database. The authors concluded that although there is a large amount of survey, observational, cohort/panel, and anecdotal evidence of phr benefits and satisfaction for patients, more research is needed to evaluate the results of phr implementations. Their in-depth analysis of the literature signalled that there is little solid evidence from randomized controlled trials or other studies through the use of phr s. Hence, they suggested that more research is needed that addresses the current lack of understanding of optimal functionality and usability of these systems, and how they can play a beneficial role in supporting patient self-management ( Archer et al., 2011 ).

9.3.4. Forms of Aggregative Reviews

Healthcare providers, practitioners, and policy-makers are nowadays overwhelmed with large volumes of information, including research-based evidence from numerous clinical trials and evaluation studies, assessing the effectiveness of health information technologies and interventions ( Ammenwerth & de Keizer, 2004 ; Deshazo et al., 2009 ). It is unrealistic to expect that all these disparate actors will have the time, skills, and necessary resources to identify the available evidence in the area of their expertise and consider it when making decisions. Systematic reviews that involve the rigorous application of scientific strategies aimed at limiting subjectivity and bias (i.e., systematic and random errors) can respond to this challenge.

Systematic reviews attempt to aggregate, appraise, and synthesize in a single source all empirical evidence that meet a set of previously specified eligibility criteria in order to answer a clearly formulated and often narrow research question on a particular topic of interest to support evidence-based practice ( Liberati et al., 2009 ). They adhere closely to explicit scientific principles ( Liberati et al., 2009 ) and rigorous methodological guidelines (Higgins & Green, 2008) aimed at reducing random and systematic errors that can lead to deviations from the truth in results or inferences. The use of explicit methods allows systematic reviews to aggregate a large body of research evidence, assess whether effects or relationships are in the same direction and of the same general magnitude, explain possible inconsistencies between study results, and determine the strength of the overall evidence for every outcome of interest based on the quality of included studies and the general consistency among them ( Cook, Mulrow, & Haynes, 1997 ). The main procedures of a systematic review involve:

• Formulating a review question and developing a search strategy based on explicit inclusion criteria for the identification of eligible studies (usually described in the context of a detailed review protocol).
• Searching for eligible studies using multiple databases and information sources, including grey literature sources, without any language restrictions.
• Selecting studies, extracting data, and assessing risk of bias in a duplicate manner using two independent reviewers to avoid random or systematic errors in the process.
• Analyzing data using quantitative or qualitative methods.
• Presenting results in summary of findings tables.
• Interpreting results and drawing conclusions.

Many systematic reviews, but not all, use statistical methods to combine the results of independent studies into a single quantitative estimate or summary effect size. Known as meta-analyses , these reviews use specific data extraction and statistical techniques (e.g., network, frequentist, or Bayesian meta-analyses) to calculate from each study by outcome of interest an effect size along with a confidence interval that reflects the degree of uncertainty behind the point estimate of effect ( Borenstein, Hedges, Higgins, & Rothstein, 2009 ; Deeks, Higgins, & Altman, 2008 ). Subsequently, they use fixed or random-effects analysis models to combine the results of the included studies, assess statistical heterogeneity, and calculate a weighted average of the effect estimates from the different studies, taking into account their sample sizes. The summary effect size is a value that reflects the average magnitude of the intervention effect for a particular outcome of interest or, more generally, the strength of a relationship between two variables across all studies included in the systematic review. By statistically combining data from multiple studies, meta-analyses can create more precise and reliable estimates of intervention effects than those derived from individual studies alone, when these are examined independently as discrete sources of information.

The review by Gurol-Urganci, de Jongh, Vodopivec-Jamsek, Atun, and Car (2013) on the effects of mobile phone messaging reminders for attendance at healthcare appointments is an illustrative example of a high-quality systematic review with meta-analysis. Missed appointments are a major cause of inefficiency in healthcare delivery with substantial monetary costs to health systems. These authors sought to assess whether mobile phone-based appointment reminders delivered through Short Message Service ( sms ) or Multimedia Messaging Service ( mms ) are effective in improving rates of patient attendance and reducing overall costs. To this end, they conducted a comprehensive search on multiple databases using highly sensitive search strategies without language or publication-type restrictions to identify all rct s that are eligible for inclusion. In order to minimize the risk of omitting eligible studies not captured by the original search, they supplemented all electronic searches with manual screening of trial registers and references contained in the included studies. Study selection, data extraction, and risk of bias assessments were performed inde­­pen­dently by two coders using standardized methods to ensure consistency and to eliminate potential errors. Findings from eight rct s involving 6,615 participants were pooled into meta-analyses to calculate the magnitude of effects that mobile text message reminders have on the rate of attendance at healthcare appointments compared to no reminders and phone call reminders.

Meta-analyses are regarded as powerful tools for deriving meaningful conclusions. However, there are situations in which it is neither reasonable nor appropriate to pool studies together using meta-analytic methods simply because there is extensive clinical heterogeneity between the included studies or variation in measurement tools, comparisons, or outcomes of interest. In these cases, systematic reviews can use qualitative synthesis methods such as vote counting, content analysis, classification schemes and tabulations, as an alternative approach to narratively synthesize the results of the independent studies included in the review. This form of review is known as qualitative systematic review.

A rigorous example of one such review in the eHealth domain is presented by Mickan, Atherton, Roberts, Heneghan, and Tilson (2014) on the use of handheld computers by healthcare professionals and their impact on access to information and clinical decision-making. In line with the methodological guide­lines for systematic reviews, these authors: (a) developed and registered with prospero ( www.crd.york.ac.uk/ prospero / ) an a priori review protocol; (b) conducted comprehensive searches for eligible studies using multiple databases and other supplementary strategies (e.g., forward searches); and (c) subsequently carried out study selection, data extraction, and risk of bias assessments in a duplicate manner to eliminate potential errors in the review process. Heterogeneity between the included studies in terms of reported outcomes and measures precluded the use of meta-analytic methods. To this end, the authors resorted to using narrative analysis and synthesis to describe the effectiveness of handheld computers on accessing information for clinical knowledge, adherence to safety and clinical quality guidelines, and diagnostic decision-making.

In recent years, the number of systematic reviews in the field of health informatics has increased considerably. Systematic reviews with discordant findings can cause great confusion and make it difficult for decision-makers to interpret the review-level evidence ( Moher, 2013 ). Therefore, there is a growing need for appraisal and synthesis of prior systematic reviews to ensure that decision-making is constantly informed by the best available accumulated evidence. Umbrella reviews , also known as overviews of systematic reviews, are tertiary types of evidence synthesis that aim to accomplish this; that is, they aim to compare and contrast findings from multiple systematic reviews and meta-analyses ( Becker & Oxman, 2008 ). Umbrella reviews generally adhere to the same principles and rigorous methodological guidelines used in systematic reviews. However, the unit of analysis in umbrella reviews is the systematic review rather than the primary study ( Becker & Oxman, 2008 ). Unlike systematic reviews that have a narrow focus of inquiry, umbrella reviews focus on broader research topics for which there are several potential interventions ( Smith, Devane, Begley, & Clarke, 2011 ). A recent umbrella review on the effects of home telemonitoring interventions for patients with heart failure critically appraised, compared, and synthesized evidence from 15 systematic reviews to investigate which types of home telemonitoring technologies and forms of interventions are more effective in reducing mortality and hospital admissions ( Kitsiou, Paré, & Jaana, 2015 ).

9.3.5. Realist Reviews

Realist reviews are theory-driven interpretative reviews developed to inform, enhance, or supplement conventional systematic reviews by making sense of heterogeneous evidence about complex interventions applied in diverse contexts in a way that informs policy decision-making ( Greenhalgh, Wong, Westhorp, & Pawson, 2011 ). They originated from criticisms of positivist systematic reviews which centre on their “simplistic” underlying assumptions ( Oates, 2011 ). As explained above, systematic reviews seek to identify causation. Such logic is appropriate for fields like medicine and education where findings of randomized controlled trials can be aggregated to see whether a new treatment or intervention does improve outcomes. However, many argue that it is not possible to establish such direct causal links between interventions and outcomes in fields such as social policy, management, and information systems where for any intervention there is unlikely to be a regular or consistent outcome ( Oates, 2011 ; Pawson, 2006 ; Rousseau, Manning, & Denyer, 2008 ).

To circumvent these limitations, Pawson, Greenhalgh, Harvey, and Walshe (2005) have proposed a new approach for synthesizing knowledge that seeks to unpack the mechanism of how “complex interventions” work in particular contexts. The basic research question — what works? — which is usually associated with systematic reviews changes to: what is it about this intervention that works, for whom, in what circumstances, in what respects and why? Realist reviews have no particular preference for either quantitative or qualitative evidence. As a theory-building approach, a realist review usually starts by articulating likely underlying mechanisms and then scrutinizes available evidence to find out whether and where these mechanisms are applicable ( Shepperd et al., 2009 ). Primary studies found in the extant literature are viewed as case studies which can test and modify the initial theories ( Rousseau et al., 2008 ).

The main objective pursued in the realist review conducted by Otte-Trojel, de Bont, Rundall, and van de Klundert (2014) was to examine how patient portals contribute to health service delivery and patient outcomes. The specific goals were to investigate how outcomes are produced and, most importantly, how variations in outcomes can be explained. The research team started with an exploratory review of background documents and research studies to identify ways in which patient portals may contribute to health service delivery and patient outcomes. The authors identified six main ways which represent “educated guesses” to be tested against the data in the evaluation studies. These studies were identified through a formal and systematic search in four databases between 2003 and 2013. Two members of the research team selected the articles using a pre-established list of inclusion and exclusion criteria and following a two-step procedure. The authors then extracted data from the selected articles and created several tables, one for each outcome category. They organized information to bring forward those mechanisms where patient portals contribute to outcomes and the variation in outcomes across different contexts.

9.3.6. Critical Reviews

Lastly, critical reviews aim to provide a critical evaluation and interpretive analysis of existing literature on a particular topic of interest to reveal strengths, weaknesses, contradictions, controversies, inconsistencies, and/or other important issues with respect to theories, hypotheses, research methods or results ( Baumeister & Leary, 1997 ; Kirkevold, 1997 ). Unlike other review types, critical reviews attempt to take a reflective account of the research that has been done in a particular area of interest, and assess its credibility by using appraisal instruments or critical interpretive methods. In this way, critical reviews attempt to constructively inform other scholars about the weaknesses of prior research and strengthen knowledge development by giving focus and direction to studies for further improvement ( Kirkevold, 1997 ).

Kitsiou, Paré, and Jaana (2013) provide an example of a critical review that assessed the methodological quality of prior systematic reviews of home telemonitoring studies for chronic patients. The authors conducted a comprehensive search on multiple databases to identify eligible reviews and subsequently used a validated instrument to conduct an in-depth quality appraisal. Results indicate that the majority of systematic reviews in this particular area suffer from important methodological flaws and biases that impair their internal validity and limit their usefulness for clinical and decision-making purposes. To this end, they provide a number of recommendations to strengthen knowledge development towards improving the design and execution of future reviews on home telemonitoring.

9.4. Summary

Table 9.1 outlines the main types of literature reviews that were described in the previous sub-sections and summarizes the main characteristics that distinguish one review type from another. It also includes key references to methodological guidelines and useful sources that can be used by eHealth scholars and researchers for planning and developing reviews.

Typology of Literature Reviews (adapted from Paré et al., 2015).

As shown in Table 9.1 , each review type addresses different kinds of research questions or objectives, which subsequently define and dictate the methods and approaches that need to be used to achieve the overarching goal(s) of the review. For example, in the case of narrative reviews, there is greater flexibility in searching and synthesizing articles ( Green et al., 2006 ). Researchers are often relatively free to use a diversity of approaches to search, identify, and select relevant scientific articles, describe their operational characteristics, present how the individual studies fit together, and formulate conclusions. On the other hand, systematic reviews are characterized by their high level of systematicity, rigour, and use of explicit methods, based on an “a priori” review plan that aims to minimize bias in the analysis and synthesis process (Higgins & Green, 2008). Some reviews are exploratory in nature (e.g., scoping/mapping reviews), whereas others may be conducted to discover patterns (e.g., descriptive reviews) or involve a synthesis approach that may include the critical analysis of prior research ( Paré et al., 2015 ). Hence, in order to select the most appropriate type of review, it is critical to know before embarking on a review project, why the research synthesis is conducted and what type of methods are best aligned with the pursued goals.

9.5. Concluding Remarks

In light of the increased use of evidence-based practice and research generating stronger evidence ( Grady et al., 2011 ; Lyden et al., 2013 ), review articles have become essential tools for summarizing, synthesizing, integrating or critically appraising prior knowledge in the eHealth field. As mentioned earlier, when rigorously conducted review articles represent powerful information sources for eHealth scholars and practitioners looking for state-of-the-art evidence. The typology of literature reviews we used herein will allow eHealth researchers, graduate students and practitioners to gain a better understanding of the similarities and differences between review types.

We must stress that this classification scheme does not privilege any specific type of review as being of higher quality than another ( Paré et al., 2015 ). As explained above, each type of review has its own strengths and limitations. Having said that, we realize that the methodological rigour of any review — be it qualitative, quantitative or mixed — is a critical aspect that should be considered seriously by prospective authors. In the present context, the notion of rigour refers to the reliability and validity of the review process described in section 9.2. For one thing, reliability is related to the reproducibility of the review process and steps, which is facilitated by a comprehensive documentation of the literature search process, extraction, coding and analysis performed in the review. Whether the search is comprehensive or not, whether it involves a methodical approach for data extraction and synthesis or not, it is important that the review documents in an explicit and transparent manner the steps and approach that were used in the process of its development. Next, validity characterizes the degree to which the review process was conducted appropriately. It goes beyond documentation and reflects decisions related to the selection of the sources, the search terms used, the period of time covered, the articles selected in the search, and the application of backward and forward searches ( vom Brocke et al., 2009 ). In short, the rigour of any review article is reflected by the explicitness of its methods (i.e., transparency) and the soundness of the approach used. We refer those interested in the concepts of rigour and quality to the work of Templier and Paré (2015) which offers a detailed set of methodological guidelines for conducting and evaluating various types of review articles.

To conclude, our main objective in this chapter was to demystify the various types of literature reviews that are central to the continuous development of the eHealth field. It is our hope that our descriptive account will serve as a valuable source for those conducting, evaluating or using reviews in this important and growing domain.

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• Cite this Page Paré G, Kitsiou S. Chapter 9 Methods for Literature Reviews. In: Lau F, Kuziemsky C, editors. Handbook of eHealth Evaluation: An Evidence-based Approach [Internet]. Victoria (BC): University of Victoria; 2017 Feb 27.
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Literature Reviews

What is a literature review.

• Getting Started
• Searching the Literature
• How to Read Scholarly Studies
• Managing Your Results
• Assembling Your Review

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• Selecting a Topic & Scope
• Identify Keywords to Use in Searching
• Finding Articles
• Reading, Note-taking, and Organization
• Citation Management

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A literature review is a very specific type of academic project. It is not an annotated bibliography. It isn't a research paper. It isn't a comprehensive list of everything ever published on a certain topic. 

Literature reviews are not created to produce new insights. They are written to explore and explain the literature on the topic or issue. 

One of the most important functions of a literature review is to lay the groundwork, provide background and context, for a larger research project such as a Masters thesis or PhD dissertation. Literature reviews often come at the start of scholarly journal articles. In the social sciences and natural sciences, a literature review comprises a section of a scholarly journal article.

Professors in research methods courses often assign standalone literature reviews so that students develop skills in searching, analyzing and organizing scholarly literature in a particular field. 

1. Selecting a Topic & Scope

The first step in any literature review is to identify a topic or subject area you wish to explore, and then setting some parameters to find the scope of your review.

You also need to make sure you select a subject area that has already been researched . It will not be possible to locate sufficient existing literature on a brand new discovery or current event that is being written about in the news right now. It needs to be a well-established research area with existing studies you can review, organize and analyze. Some professors require you to find a topic that has 'not been researched before'. In that case, they don't mean an entire broad topic that hasn't been researched; instead, you'll want to find a sliver of a broad topic that hasn't been researched before. This is where narrowing your topic and finding parameters becomes very important. You may need to do some background reading on several different topics to find one that works, if your professor is having you do a standalone literature review as part of a research methods course.

Ways of Narrowing a Broad topic

For example:

Broad topic: ADHD treatments

Narrowed question: How can neurofeedback be used in threating elementary school-aged children?

Publication Dates

The scope of your review will be a part of refining your topic area or research question. In some disciplines, medicine and health science for example, the publication date of your sources may be extremely important. So, to avoid including outdated clinical recommendations, you may want to limit your review to only the most recent research out there. For other topics, say history or literature, publication date may not be as important - and scholarly research from 20, 30, even 50 years ago may still be relevant and useful today. So it's good idea to consider setting some date ranges for your search, it that is important to your topic.

Whatever your topic area turns out to be, framing the boundaries of your research question ahead of time will make searching and selecting appropriate articles that much easier. 

2. Identify Keywords to Use in Searching

Once you have defined a suitable topic or research question for your review, you will need to create a list of keywords that you will use to search for appropriate studies to include in your review. You will be doing searches through several different databases, Google scholar, or publisher platforms and the terminology used in each may vary. It is especially important to have a good variety of search terms that you can combine in different ways. This will ensure you gather the most relevant sources that cover your topic thoroughly. 

Remember to continue to gather and change your keywords as you read more about your topic!

To start, list synonyms and phrases that have to do with the main words of a research topic:

Example: Is neurofeedback useful in the treatment of ADHD in children?

Now, let's consider the word "useful" in this example topic. What is meant by "useful"? The word itself will not be helpful while searching. Instead, think about what might be useful  in terms of treatment of a child with ADHD. Think about benefits and outcomes and brainstorm a list of words:

3. Finding Articles

Using research guides to find subject specific databases.

For more focused searching of the literature of just one discipline, head over to the Research Guides section of our website. We have  Subject Guides   for all disciplines represented at UTC. Find the subject guide that has most to do with your topic, for example, if you are writing about politics, you'd choose Political Science and Public Service guide. Writing about K-12 schools? Choose Education. Each Subject Guide was created by UTC Librarians and has links to a variety of resources that you have access to.

The databases listed are smaller, specialized search engines that mainly retrieve scholarly articles. You will usually find smaller sets of results for each search you do, but those results will be from a subset of very focused resources.

Subject specific databases are searchable by keywords just like Quick Search. An example is shown in the screenshot below of the APA PsycINFO database using the keywords "neurofeedback therapy" AND "ADHD in children":

APA PsycInfo Database Search:

Using the Quick Search

Quick Search is the main search box located in the center of the Library home page. It covers all formats within our collection (physical and electronic, books, films, articles and more).and all subject areas. It is an excellent tool for locating and accessing scholarly content using keyword searches. Below is an example of how to enter your keywords for an effective search, for our sample topic we typed the words "neurofeedback ADHD children behavior problems":

Quick Search has filters  to narrow to just peer reviewed if you'd like, or you can narrow to a specific format like articles, books, or ebooks. You can also narrow by date. Look for the filters on the left sidebar after you run a search. 

As you browse results. you will notice links below each article that allow you to read the full text on the publisher website. If you decide you would like to use the article in your lit review, download the entire PDF to your device for later use. 

Using Google Scholar

Click the  Databases button (just below the Quick Search box on library's homepage) and look for Google Scholar under Multisubject Databases. Using Google Scholar through the UTC Library links our library subscriptions to your Google Scholar search results- which allows you to see articles with no paywalls if we have access! 

4. Reading, Note-taking, and Organization

1. review the how to read a scholarly article guide.

• Learn about common sections in science and social science articles
• Strategies and tips for reading start by reading the entire Abstract, and feel free to jump down to Discussion to decide if an article should be included in your paper

2. Save yourself time with good note-taking

As you read each study, take notes about the most important findings, key concepts, debates or areas of controversy and common themes you see. These notes will inform how you approach organizing and writing your literature review.

To keep organized, UTC Librarians recommend using a literature review matrix, or spreadsheet, to keep track of the articles you find as you go.  Add columns for the citation (including the URL of the article), and once you read it, track the authors' research question, methods, findings and themes. Importantly, keep track of notes and quotes as you go, and the page numbers you got them from. You will see themes or facts emerge as you read more and more articles. 

Here's an example Literature Review Matrix for you to view. Download a sample matrix as an Excel file and edit with your own sources.

3. Some ideas on how to compile an outline for your review:

After reading and taking notes on the sources you are including in your literature review, you will probably be able to identify common themes or threads that appear throughout. These recurring threads or themes can be very useful in creating a narrative framework for your review to make it easier for your readers to understand what literature exists, what has been learned, and why it is significant. Using our example of Neurofeedback Therapy for Children with ADHD, we might decide to organize our results something like this:

Other questions you might ask yourself as you decide how to outline your literature review: 

• What are the major claims being made about the topic? (There may be several)
• What significant data exists to support / explain the claims?
• Are there connections between the claims / concepts / evidence?
• Are there controversies in the literature? 
• Are there knowledge gaps that have yet to be explored? 

5. Citation Management

For smaller literature review projects, simply keeping a list of your references in Word or Google Docs is probably fine. But for longer projects, or those that are going to form the basis for a thesis or dissertation, many students choose to use citation management software to keep track of, organize, and format their references. The UTC Library supports two main citation management options: Zotero and EndNote. 

Zotero is an open source tool provided by Google. It works well with Chrome and Google Docs and has a really nice, easy to use Chrome extension that allows you to seamlessly add references and full text PDFs to your reference "library" as you do your research. The Library has a guide page that walks you through the basics of downloading, configuring and using Zotero. Visit the link below to get started. 

Zotero Guide Page

EndNote is a very powerful software package with lots of advanced features. It is produced by a commercial publisher and the Library pays a subscription fee to offer it to our students and faculty. It comes in two versions: desktop and cloud-based. (The two versions work together to provide seamless access and redundancy no matter where you are). EndNote can be very labor intensive to configure and use at the beginning, but it offers hundreds of citation styles (most major journals, academic associations and scholarly publishers) and works very well for longer, more complex projects with many references and citations. It integrates really well with Microsoft Word but does not work as well with Google Docs. The Library has basic information on its website about how to download and set up EndNote, but in order to learn it effectively, a workshop or librarian consultation is usually required. Our EndNote information is found a the link below:

EndNote Help Page

The UTC Library is home to a full-service Writing and Communication Center with tutors available to assist you with writing projects at any stage - from outline, to draft, to final manuscript. The WCC has it's own section of the UTC Library website. Check out the link below to learn more about the services they offer and how to go about scheduling an appointment.

UTC Writing and Communication Center

• Next: Getting Started >>
• Last Updated: Sep 19, 2023 8:50 AM
• URL: https://guides.lib.utc.edu/literature-reviews

A Step-by-Step Guide to Writing a Stellar Literature Review (with Help from AI)

Table of contents

Aren’t all of us mini versions of Sherlock Holmes when browsing data and archives for a research piece? As we go through the process, a comprehensive literature review is an essential toolkit to make your research shine.

A literature review consists of scholarly sources that validate the content. Its primary objective is to offer a concise summary of the research and to let you explore relevant theories and methodologies. Through this review, you can identify gaps in the existing research and bridge them with your contribution. 

The real challenge is how to write an excellent literature review. Let’s learn.

What is the purpose of a literature review?

A literature review is an introduction to your research. It helps you put your perspective to the table, along with a summary of the theme.

What does my literature review communicate?

• Explanation of your research: how the information was collected, the research method, the justification of the chosen data sources, and an overview of the data analysis.
• Framework: the journey from where the concept began and how it is presented.
• Connects the previous and current research: 

It presents the broader scope of your research by connecting it to the existing data and debates and underlining how your content fits the prevailing studies. 

In an era of information overload, a literature review must be well-structured. 

Let’s learn all about the structure and style of a literature review that’ll help you strengthen your research.

Literature review– structure and style

Begin with a question and end it with the solution– the key to structuring a literature review. It resembles an essay’s format, with the first paragraph introducing the readers to the topic and the following explaining the research in-depth.

The conclusion reiterates the question and summarizes the overall insights of your research. There’s no word count restriction. —it depends on the type of research. For example, a dissertation demands lengthy work, whereas a short paper needs a few pages. 

In a literature review, maintaining high quality is vital, with a focus on academic writing style. Informal language should be avoided in favor of a more formal tone. 

The content avoids contractions, clearly differentiating between previous and current research through the use of past and present tense. Wordtune assists in establishing a formal tone, enhancing your work with pertinent suggestions. This AI-powered tool ensures your writing remains genuine, lucid, and engaging. 

The option of refining the tonality offers multiple possibilities for rephrasing a single sentence. Thus, pick the best and keep writing.

Get Wordtune for free > Get Wordtune for free >

Your friendly step-by-step guide to writing a literary review (with help from AI)

Do you find it challenging to begin the literature review? Don’t worry! We’re here to get you started with our step-by-step guide.

1. Narrow down the research scope

Simply begin with the question: What am I answering through my research?

Whether it’s cooking or painting, the real challenge is the prep-up for it rather than performing the task. Once you’re done, it smoothly progresses. Similarly, for your literature review, prepare the groundwork by narrowing down the research scope.

Browse and scoop out relevant data inclining well with your research. While you can’t cover every aspect of your research, pick a topic that isn’t too narrow nor too broad to keep your literature review well-balanced. 

2. Hunt relevant literature

The next question: Does this data align with the issue I’m trying to address?

As you review sources of information, hunt out the best ones. Determine which findings help in offering a focused insight on your topic. The best way to pick primary sources is to opt for the ones featured in reliable publications. You can also choose secondary sources from other researchers from a reasonable time frame and a relevant background.

For example, if your research focuses on the Historical Architecture of 18th-century Europe, the first-hand accounts and surveys from the past would hold more weight than the new-age publications. 

3. Observe the themes and patterns in sources

Next comes: What is the core viewpoint in most of the research? Has it stayed constant over time, or have the authors differed in their points of view?

Ensure to scoop out the essential aspects of what each source represents. Once you have collected all this information, combine it and add your interpretations at the end. This process is known as synthesis.

Synthesize ideas by combining arguments, findings and forming your new version.

4. Generate an outline

The next question: How can I organize my review effectively? When navigating multiple data sources, you must have noticed a structure throughout the research. Develop an outline to make the process easier. An outline is a skeletal format of the review, helping you connect the information more strategically.

Here are the three different ways to organize an outline– Chronologically, Thematically, or by Methodology.You can develop the outline chronologically, starting from the older sources and leading to the latest pieces. Another way of organizing is to thematically divide the sections and discuss each under the designated sub-heading.

You can even organize it per the research methods used by the respective authors. The choice of outline depends on the subject. For example, in the case of a science paper, you can divide the information into sections like introduction, types of equipment, method, procedure, findings, etc. In contrast, it’s best to present it in divisions based on timelines like Ancient, Middle Ages, Industrial revolutions, etc., for a history paper.

If you’re confused about how to structure the data, work with Wordtune. 

With the Generate with AI feature, you can mention your research topic and let Wordtune curate a comprehensive outline for your study.

Having a precise prompt is the key to getting the best results.

5. Start filling!

Your next question must be: Am I ready to compose all the parts of the literature review?

Once you’re ready with the basic outline and relevant sources, start filling in the data. Go for an introductory paragraph first to ensure your readers understand the topic and how you will present it. Ensure you clearly explain the section in the first sentence.

However, if beginning from the first paragraph seems intimidating, don’t worry! Add the main body content to the sub-headings, then jump to the introduction. 

Add headings wherever possible to make it more straightforward and guide your readers logically through different sources. Lastly, conclude your study by presenting a key takeaway and summarizing your findings. To make your task easier, work with Wordtune. It helps align your content with the desired tone and refine the structure.

6. Give attention to detail and edit

The last question: Am I satisfied with the language and content written in the literature review? Is it easy to understand?

Once you’re done writing the first draft of a literature review, it’s time to refine it. Take time between writing and reading the draft to ensure a fresh perspective. It makes it easier to spot errors when you disconnect from the content for some time. Start by looking at the document from a bird's eye to ensure the formatting and structure are in order. 

After reviewing the content format, you must thoroughly check your work for grammar, spelling, and punctuation. One of the best approaches to editing and proofreading is to use Wordtune . It helps simplify complex sentences, enhance the content quality, and gain prowess over the tonality.

The dos and don’ts of writing a literature review

Writing a stellar literature review requires following a few dos and don'ts. Just like Sherlock Holmes would never overlook a hint, you must pay attention to every minute detail while writing a perfect narrative. To help you write, below are some dos and don'ts to remember.

Composing a literature review demands a holistic research summary, each part exhibiting your understanding and approach. As you write the content, make sure to cover the following points:

• Keep a historical background of the field of research. Highlight the relevant relation between the old studies and your new research.
• Discuss the core issue, question, and debate of your topic.
• Theories lay the foundation of research. While you’re writing a literature review, make sure to add relevant concepts and ideas to support your statements.
• Another critical thing to keep in mind is to define complex terminologies. It helps the readers understand the content with better clarity. 

Examples of comprehensive literature reviews

Aren’t good examples the best way to understand a subject? Let’s look into a few examples of literature reviews and analyze what makes them well-written.

1. Critical Thinking and Transferability: A Review of the Literature (Gwendolyn Reece)

An overview of scholarly sources is included in the literature review, which explores critical thinking in American education. The introduction stating the subject’s importance makes it a winning literature review. Following the introduction is a well-defined purpose that highlights the importance of research.

As one keeps reading, there is more clarity on the pros and cons of the research. By dividing information into parts with relevant subheadings, the author breaks a lengthy literature review into manageable chunks, defining the overall structure.

Along with other studies and presented perspectives, the author also expresses her opinion. It is presented with minimal usage of ‘I,’ keeping it person-poised yet general. Toward the conclusion, the author again offers an overview of the study. A summary is further strengthened by presenting suggestions for future research as well. 

2. The Use of Technology in English Language Learning: A Literature Review

This literature review is thematically organized on how technology affects language acquisition. The study begins with an introduction to the topic with well-cited sources. It presents the views of different studies to help readers get a sense of different perspectives. After giving these perspectives, the author offers a personalized opinion.

One of the critical aspects that makes this a good literature review is a dedicated paragraph for definitions. It helps readers proceed further with a clear understanding of the crucial terminologies. There’s a comparison of the modern and previous studies and approaches to give an overall picture of the research.

Once the main body is composed, the author integrates recommendations for action-based tips. Thus, the literature review isn’t just summarizing the sources but offering actions relevant to the topics. Finally, the concluding paragraph has a brief overview with key takeaways.

Wordtune: your writing buddy!

A literature review demands the right balance of language and clarity. You must refine the content to achieve a formal tone and clear structure. Do you know what will help you the most? Wordtune !. 

The real-time grammar checker leaves no scope for errors and lets you retain precision in writing. This writing companion is all you need for stress-free working and comprehensive literature review development.

Let the narrative begin

A literary review isn't just about summarizing sources; it's about seamlessly bringing your perspective to the table. Always remember to set a narrative for added interest and a brilliant composition. With structure and style being the pillars of a stellar literature review, work with Wordtune to ensure zero compromises on the quality.

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The Scope and Impact of Viral Infections in Common Variable Immunodeficiency (CVID) and CVID-like Disorders: A Literature Review

Affiliations.

• 1 Department of Clinical Immunology and Allergy, Leeds Teaching Hospitals NHS Trust, Leeds LS9 7TF, UK.
• 2 Leeds Institute of Rheumatic and Musculoskeletal Medicine (LIRMM), School of Medicine, University of Leeds, Chapel Allerton Hospital, Chapeltown Road, Leeds LS7 4SA, UK.
• 3 Allergy and Clinical Immunology Unit, University Clinic Golnik, 36 Golnik, 4204 Golnik, Slovenia.
• 4 Faculty of Medicine, University of Ljubljana, Vrazov Trg 2, 1000 Ljubljana, Slovenia.
• PMID: 38541942
• DOI: 10.3390/jcm13061717

Common Variable Immunodeficiency (CVID) is a heterogeneous primary immunodeficiency disorder characterised by impaired antibody production, leading to recurrent infections and an increased susceptibility to viral pathogens. This literature review aims to provide a comprehensive overview of CVID's relationship with viral infections, encompassing disease pathogenesis, key presenting features, specific monogenic susceptibilities, the impact of COVID-19, and existing treatment options. The pathogenesis of CVID involves complex immunological dysregulation, including defects in B cell development, antibody class switching, and plasma cell differentiation. These abnormalities contribute to an impaired humoral immune response against viral agents, predisposing individuals with CVID to a broad range of viral infections. Genetic factors play a prominent role in CVID, and monogenic drivers of CVID-like disease are increasingly identified through advanced genomic studies. Some monogenic causes of the CVID-like phenotype appear to cause specific viral susceptibilities, and these are explored in the review. The emergence of the COVID-19 pandemic highlighted CVID patients' heightened predisposition to severe outcomes with viral infections. This review explores the clinical manifestations, outcomes, and potential therapeutic approaches for COVID-19 in CVID patients. It assesses the efficacy of prophylactic measures for COVID-19, including vaccination and immunoglobulin replacement therapy, as well as trialled therapies.

Keywords: COVID-19; CVID; NFKB1; NFKB2; chronic norovirus; common variable immunodeficiency; monogenic CVID; oncoviruses; viral gastroenteritis; viral hepatitis; viral infections.

Publication types