How to Write a Literature Review That Synthesises Sources

Most students know they need to "review the literature", but the hardest part is not finding sources. It is turning a stack of reading into a piece of writing with its own argument.

This guide explains what a literature review does, how to search and organise, how to structure the chapter, and how to write paragraphs that synthesise rather than summarise.

What a literature review does

A literature review can be a chapter of a dissertation, a section of a research paper or proposal, or a standalone assignment. In each case it has the same core jobs:

• show what is already known about your topic;
• identify patterns, agreements, disagreements and weaknesses in that research;
• explain the key theories or concepts your work will use;
• reveal a gap or problem that justifies your study.

What markers look for

Markers usually reward synthesis (connecting sources to each other), evaluation (judging the quality and limits of studies), relevance (staying close to your question) and structure (a logical route through the field). Description alone, however accurate, tends to receive lower marks.

How to write a literature review, step by step

1. Define your scope

Write down your research question or topic and decide your boundaries: time period, disciplines, geographical focus and types of source. Clear boundaries stop you reading endlessly and make your choices defensible.

2. Search systematically

Use your library's databases as well as general search engines. Build search terms from your key concepts and their synonyms, and combine them with AND, OR and quotation marks. Keep a short record of which databases and terms you used, as some departments ask you to report this.

Useful strategies include checking the reference lists of key papers (backward searching) and seeing who has cited them since (forward searching).

3. Record sources in a matrix

As you read, note each source's context, method, main findings and limitations in one table. This makes comparison much easier when you write.

Illustrative layout only. Fill it with the real sources from your own reading.

4. Look for themes and tensions

Read across the rows of your matrix. Which ideas appear repeatedly? Where do findings conflict? Are certain methods or contexts over-represented? These patterns become your themes and point towards the gap.

5. Choose a structure

There are several common ways to organise a review:

• Thematic: sections based on themes or debates. This is the most common and usually the strongest for dissertations.
• Methodological: sections based on how studies were conducted, useful when method strongly shapes findings.
• Chronological: sections showing how thinking developed over time. Use with care, as it can slip into description.
• Theoretical: sections organised around competing theories or models.

Many reviews combine approaches, for example thematic sections with brief attention to how the debate developed.

6. Write synthesis paragraphs

A useful pattern for each paragraph is: make a point, bring in several sources that support, qualify or challenge it, evaluate them, and explain what this means for your question.

7. Conclude by leading to your study

End the review by summarising what is known, what remains unclear and how your research question responds to that. This creates a smooth bridge to your methodology.

Common mistakes

• One paragraph per source. This produces an annotated bibliography, not a review.
• No evaluation. Treating every study as equally strong, without commenting on sample, method or context.
• Drifting off topic. Including interesting material that does not relate to your question.
• Over-reliance on quotations. Paraphrasing and comparing shows understanding; long quotes hide it.
• Ignoring contradictory evidence. Leaving out studies that disagree with your expectations weakens credibility.
• No clear end point. A review that stops without identifying a gap leaves your research question unsupported.

Literature review checklist

• My scope (time, context, source types) is clear and justified.
• I can explain my search strategy if asked.
• Each section is organised around a theme or debate, not a single author.
• Most paragraphs cite and compare more than one source.
• I comment on the strengths and limitations of key studies.
• Conflicting findings are acknowledged and discussed.
• The review ends by stating the gap and linking to my research question.
• Every in-text citation appears correctly in my reference list.

Frequently asked questions

How many sources should a literature review include?

There is no fixed number. It depends on your level, word limit, discipline and how much research exists on your topic. Focus on covering the key studies and debates well rather than reaching a target, and ask your supervisor if your department has expectations.

Can I use older sources?

Yes, particularly for foundational theories or influential studies. Most reviews combine key older works with recent research to show how the field has developed. If almost all your sources are old, check whether you have missed newer work.

What is the difference between a literature review and a systematic review?

A systematic review follows a formal, pre-defined protocol for searching, screening and appraising studies, and reports these steps in detail. A typical dissertation literature review is more flexible, although a clear and documented search approach still strengthens it. Some programmes ask for a systematic or scoping review as the whole project, in which case specific reporting guidelines usually apply.

Should I write the literature review before collecting data?

Usually you write a substantial draft first, because it shapes your question and method. Many students return to it later to add sources relevant to unexpected findings, and to make sure it connects to the discussion chapter.

Help with your review

If your review reads more like a list than an argument, our literature review guidance can give feedback on structure and synthesis while you remain the author. To organise your reading, try the free literature review matrix.