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Before you start to think about what to include in your review, it is useful to think broadly about the types of literature that exist.

Wallace and Wray (2016) describe the following types of literature:

  • Theoretical literature
  • Research literature
  • Practice literature
  • Policy literature.

Depending on your discipline, some types of literature might not fit easily into the above categories. Consider the following examples:

  • Archival sources
  • Critical literature.
 Useful information Useful information

Classifying academic literature is not an end in itself, but it will help you to identify the type of literature you need for your study.

Click 'Next' to move through the screens and find out more about the different categories of literature.

Continue on to find out more about the different categories of literature.

Theoretical literature

The term 'theory' is generally taken to mean a construct about what the world is like. Theoretical knowledge is often developed on the basis of our empirical observations of the world. For example, when HIV/AIDS was first identified in the late 1970s and 80s, various theories were developed about the route of transmission and causation, on the basis of observations made about the disease. It was only later, when the disease had been thoroughly investigated, that many of these theories were disproved.

Theories are not always based on evidence – for example, the theory that the world is flat was based upon the beliefs of ancient cultures. It was not until advances in science led to the discovery that the world was round that the theory was disproved.

Research literature

A research study is generally understood to be a report of a systematic investigation which has been undertaken in response to a specific research question. For some research studies empirical data will be collected, while for others the data collected will be in the form of historical documents or literary texts. The research question will often arise from a particular theory in an attempt to prove or disprove it.

When undertaking a literature review, it is your job to identify what is research and what is not. When you encounter literature that you would classify as research literature, you need to identify the type of method used to carry out the research and assess the quality of evidence the research literature provides.

Practice literature

Practice literature is written by practitioners about their fields of expertise. Expert opinion, discussion articles and papers about 'how to...' are likely to abound in your area of interest. These may be published observations and ideas about practice-related issues. Be warned: some practice literature might overlap with what you would classify as research and you need to be clear about whether the literature represents practice or research. You can do this mainly by assessing the extent to which there is a systematic approach to the collection of data which is then used to draw conclusions.

For example, Anne Frank's diary is a detailed documentation of the life of a young girl living in hiding in the the Second World War. Since being published, the diary has become one of the most important and well-known pieces of evidence of the experience of those in hiding.

Policy literature

Policy literature is literature that tells practitioners or professionals how to act. Policy literature can be based on theory, research or practice and it is your job to examine the policy to discern the basis for its advice or instructions. For example, a policy that is based on research is likely to carry more weight than a policy based on theory alone. Similarly, a policy that is based on the professional opinion or practice-based literature of a group of professionals is likely to carry less weight than one based on research. If policy documents are an important part of your literature review, it is useful to consider how they were constructed and on what basis they were established.


Adapted from Wallace and Wray (2016: 19–21)

Archival sources

Archival literature can include public and private documents, artefacts, internal bureaucratic documents, letters, notes, receipts, diaries, photographs, etc. If archival sources are part of your research and literature review, you will need to consider carefully when, where, why and by whom they were constructed, and how they affected your subject.

Archival literature can usually be regarded as practice literature but the emphasis is that the documents are archived sources.

Critical literature

Critical literature can also be referred to as secondary sources in your literature review. It comprises the theorised critical analysis of your primary sources by other people, such as literary critics, historians and scientists. It can include published articles in journals and other news outlets, books, blogs, reviews, etc. You need to acknowledge when another critical voice has engaged with your subject and enter into dialogue with it, developing your own critical perspective.

Wisker (2018)

Theoretical literature

The term 'theory' is generally taken to mean a construct about what the world is like. Theoretical knowledge is often developed on the basis of our empirical observations of the world. For example, when HIV/AIDS was first identified in the late 1970s and 80s, various theories were developed about the route of transmission and causation, on the basis of observations made about the disease. It was only later, when the disease had been thoroughly investigated, that many of these theories were disproved.

Theories are not always based on evidence – for example, the theory that the world is flat was based upon the beliefs of ancient cultures. It was not until advances in science led to the discovery that the world was round that the theory was disproved.

Research literature

A research study is generally understood to be a report of a systematic investigation which has been undertaken in response to a specific research question. For some research studies empirical data will be collected, while for others the data collected will be in the form of historical documents or literary texts. The research question will often arise from a particular theory in an attempt to prove or disprove it.

When undertaking a literature review, it is your job to identify what is research and what is not. When you encounter literature that you would classify as research literature, you need to identify the type of method used to carry out the research and assess the quality of evidence the research literature provides.

Practice literature

Practice literature is written by practitioners about their fields of expertise. Expert opinion, discussion articles and papers about 'how to...' are likely to abound in your area of interest. These may be published observations and ideas about practice-related issues. Be warned: some practice literature might overlap with what you would classify as research and you need to be clear about whether the literature represents practice or research. You can do this mainly by assessing the extent to which there is a systematic approach to the collection of data which is then used to draw conclusions.

For example, Anne Frank's diary is a detailed documentation of the life of a young girl living in hiding in the the Second World War. Since being published, the diary has become one of the most important and well-known pieces of evidence of the experience of those in hiding.

Policy literature

Policy literature is literature that tells practitioners or professionals how to act. Policy literature can be based on theory, research or practice and it is your job to examine the policy to discern the basis for its advice or instructions. For example, a policy that is based on research is likely to carry more weight than a policy based on theory alone. Similarly, a policy that is based on the professional opinion or practice-based literature of a group of professionals is likely to carry less weight than one based on research. If policy documents are an important part of your literature review, it is useful to consider how they were constructed and on what basis they were established.

Adapted from Wallace and Wray (2016: 19–21)

Archival sources

Archival literature can include public and private documents, artefacts, internal bureaucratic documents, letters, notes, receipts, diaries, photographs, etc. If archival sources are part of your research and literature review, you will need to consider carefully when, where, why and by whom they were constructed, and how they affected your subject.

Archival literature can usually be regarded as practice literature but the emphasis is that the documents are archived sources.

Critical literature

Critical literature can also be referred to as secondary sources in your literature review. It comprises the theorised critical analysis of your primary sources by other people, such as literary critics, historians and scientists. It can include published articles in journals and other news outlets, books, blogs, reviews, etc. You need to acknowledge when another critical voice has engaged with your subject and enter into dialogue with it, developing your own critical perspective.

Wisker (2018)

These classifications provide a useful approach for the early stages in a literature review, when it is important to begin to consider what different types of literature there are and how they are used within scholarly work.

Given the vast range of literature available, it is vital that you include the most relevant literature in your review.

 Useful information Useful information

There are many different ways in which a research study can be undertaken. Some approaches involve numerical measurement; other approaches involve description and do not attempt to quantify the information they collect. Some approaches collect data from animal subjects and others might be literature based and involve the systematic review of literary/historical/scientific texts relating to the topic of research.

Decide what type of literature would be most relevant for each of the following research studies. Drag and drop the studies into the appropriate column, and then read the feedback.

Decide what type of literature would be most relevant for each of the following research studies by placing the items provided in the groups provided. Continue on for feedback.

 Theoretical literature

You are looking at the political ideologies that shaped thinking in early 20th-century Europe.

Political ideologies

 The political theories that shaped thinking in 20th-century Europe would be the basis for this review. Research literature

Your research is looking at ways to promote adherence to hand-hygiene policy within local restaurants and cafes. One focus of your literature review is to establish what is known about adherence to hand-hygiene policies.

Adherence to hand-hygiene policy

 The best type of literature for this study is research literature that has incorporated a direct observational method. Any other approach, for example asking catering staff whether they always wash their hands in the course of their work, is likely to be less accurate. Practice literature

Your research project is to explore the rise of feminism through the eyes of the women involved during the early 1900s.

Feminism in the early 1900s

 The most important literature for this study would be first-hand accounts of feminism from that time. Second-hand accounts, although they might provide useful data, would not be the top priority. Policy literature

You are looking at the ways in which the working lives of women were restricted by laws in the time of the Suffragettes.

Working lives of women

 The policies that were in place in the time of the Suffragettes and that denied women voting and other rights and privileges would be the focus of this review. Archival sources

You are looking at the influences of sustainability, ecology and indigenous knowledge on Margaret Atwood's writing.

Atwood and sustainability

 The sources for this literature review are documents on sustainability, interviews with indigenous leaders and Atwood's own letters about sustainability and sound ecological behaviours in relation to her writing. Critical literature

You are looking at the elements of Gothic fiction in Toni Morrison's novels.

Gothic writing

 The most important texts for this literature review are critical essays, articles, books and blogs which analyse Morrison's writing from a Gothic perspective.

Here are the groups you are asked to place items into:

  • Theoretical literature
  • Research literature
  • Practice literature
  • Policy literature
  • Archival sources
  • Critical literature

Considering these groups, think about which group each of the following items belongs in:

  • Your research is looking at ways to promote adherence to hand-hygiene policy within local restaurants and cafes. One focus of your literature review is to establish what is known about adherence to hand-hygiene policies.
  • You are looking at the influences of sustainability, ecology and indigenous knowledge on Margaret Atwood's writing.
  • You are looking at the elements of Gothic fiction in Toni Morrison's novels.
  • You are looking at the ways in which the working lives of women were restricted by laws in the time of the Suffragettes.
  • You are looking at the political ideologies that shaped thinking in early 20th-century Europe.
  • Your research project is to explore the rise of feminism through the eyes of the women involved during the early 1900s.

The correct answers are:

  • Theoretical literature
    • You are looking at the political ideologies that shaped thinking in early 20th-century Europe.
      Feedback: The political theories that shaped thinking in 20th-century Europe would be the basis for this review.
  • Research literature
    • Your research is looking at ways to promote adherence to hand-hygiene policy within local restaurants and cafes. One focus of your literature review is to establish what is known about adherence to hand-hygiene policies.
      Feedback: The best type of literature for this study is research literature that has incorporated a direct observational method. Any other approach, for example asking catering staff whether they always wash their hands in the course of their work, is likely to be less accurate.
  • Practice literature
    • Your research project is to explore the rise of feminism through the eyes of the women involved during the early 1900s.
      Feedback: The most important literature for this study would be first-hand accounts of feminism from that time. Second-hand accounts, although they might provide useful data, would not be the top priority.
  • Policy literature
    • You are looking at the ways in which the working lives of women were restricted by laws in the time of the Suffragettes.
      Feedback: The policies that were in place in the time of the Suffragettes and that denied women voting and other rights and privileges would be the focus of this review.
  • Archival sources
    • You are looking at the influences of sustainability, ecology and indigenous knowledge on Margaret Atwood's writing.
      Feedback: The sources for this literature review are documents on sustainability, interviews with indigenous leaders and Atwood's own letters about sustainability and sound ecological behaviours in relation to her writing.
  • Critical literature
    • You are looking at the elements of Gothic fiction in Toni Morrison's novels.
      Feedback: The most important texts for this literature review are critical essays, articles, books and blogs which analyse Morrison's writing from a Gothic perspective.

Considering the literature that is available within these core categories is an effective way of conceptualising a large volume of available published work. This will help you in the process of critical appraisal or evaluation, which we will consider in the module Evaluation of the literature.

Remember that not all of the literature you encounter will fit neatly into these categories. There may be some blurring of the boundaries and you might develop new categories to describe the literature you use.