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Literature review: Search strategy design


NB: Databases have different interfaces; use the Help and Tutorials to learn how to apply the following techniques to each database

Inclusions and exclusions

Once you have identified the type of literature you need in your review, you need to define the inclusion and exclusion criteria which will inform your literature search. 

Common examples of inclusion and exclusion criteria

  • Time frame
  • Language or country
  • Main focus of paper
  • Methodology or outcomes
  • Type of literature (e.g. only peer-reviewed journal articles) 
  • Location of literature (e.g. only studies available in a particular set of databases)

See Epigeum tutorial Research Methods in Literature Review on Blackboard GST1 for more information and an example of using inclusion and exclusion criteria.

See also



Keywords and Subject headings

Using Keywords – Free-Text/Natural Language Searching

A keyword is a word or phrase, significant to your search topic, which will enable you to retrieve references. A keyword search uses ‘free text’ to identify all records containing the word or words that you enter in your search field. Results may come from within any part of the record e.g. title; abstract; subject heading within library catalogues, databases and websites. However, websites rely almost exclusively on ‘free text’ searching while databases will be more likely to be indexed using controlled vocabulary.

Using Subject headings / Thesauri / Controlled Vocabulary - Searching

A controlled vocabulary thesaurus is a set of pre-defined terms assigned to describe the content of an article. A controlled vocabulary search will map the ‘free text’ word or phrase to the controlled vocabulary heading/term. For example, Mesh (Medical Subject Headings) is the U.S. National Library of Medicine’s controlled vocabulary and is used to index Medline and PubMed. Using Pre-defined headings/terms will enable you to conduct a more precise search, based on the structured language of the database. 

Handy tip:

Look at subject indexing for a key reference and use to modify your search terms

An introduction to subject headings


A tutorial on Subject headings and how to use them in your search from Taylor Library, Western University: 

Using subject headings on the library catalogue

You may use subject headings on the library catalogue to find books on a particular topic very quickly. See screenshot below showing how to use the Browse button to find books on writing a thesis by selecting subject field.

Tutorials on searching using subject headings


This tutorial demonstrates how to browse the Subject Terms in Academic Search Complete as well as how to create database searches using subject terms.


A more detailed tutorial showing how and why to use a thesaurus from PsycINFo, which can be applied to using other database thesauri:


Other search techniques

Phrase searching

Phrase Searching allows you to use a string of words instead of a single one. Many databases allow you to search for an exact phrase such as Climate Change or Genetically Modified Organisms. Results found will highlight the phrase exactly as typed. However, some databases will require the use of Inverted Commas while others will require the use of brackets. You are advised to check the HELP section of each database.

“Male Breast Cancer” is an example of Phrase Searching


Using a truncation character allows you to broaden your search by retrieving varying endings of your search term. For example, in the database Web of Science, a search for Child* will retrieve documents that mention Child, Children, Childcare, Children’s, Childhood. Check the HELP section of each database to find the truncation character to use.


Related to truncation are Wildcards which help you search for internal variations of spelling within your search term. An example in Web of Science is wom?n which will retrieve articles that mention women and woman. Wildcards are also useful in dealing with American spelling variations. For example computeri?ation finds computerisation and computerization. Check the HELP section of each database to find the wildcard character to use.

Proximity operators

Proximity searching is a way of narrowing your search using different operators. For example, on Scopus:

  •  W/n restricts to n words between the two words, the word order is not set Pain W/5 morphine
  • Pre/n restricts to n words between the two words, the word order is as set newborn PRE/3 screening


Again, you are advised to check the HELP section of each database as proximity operators vary on different databases.

See online tutorial below demonstrating these search techniques on Web of Science:

Build Better Searches in Web of Science 5 minute video tutorial

Combining terms using Boolean operators

The principles of Boolean Logic enable you to relate concepts to one another in sets. Consisting of the 3 logical operators or connectors, AND, OR, NOT, Boolean operators allow you to more efficiently link 2 or more terms, thereby retrieving more precise results.

AND narrows a search; OR broadens it, while NOT excludes references, containing specified search terms, from your results. These operators may need to be entered in upper case in some databases.



Combining terms using Boolean operators - online tutorials

Other ways of searching


  • Follow up references from reference lists of relevant articles
  • Identify key journals and conference proceedings in your field and browse them cover to cover (handsearching)
  • Identify key authors and check for other relevant publications and current research

Search results - sorting and filtering to refine your search

Most databases allow you to:

  • sort your results by date, relevance, author etc
  • filter your results by e.g. publication type such as reviews, books etc

Sample search strategy


See a sample search strategy incorporating various search techniques at


Review your search strategy


Now review your search strategy using the Search Strategy Worksheet incorporating search techniques from this section:




(From program developed by librarians from Ohio universities)