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Literature reviews: Searching

“Ensure that your main search is adequately balanced in terms of specificity (it identifies the relevant evidence) and sensitivity (it does not identify too many irrelevant sources”

Boland et al., Doing a systematic review: a student's guide.

The next step is to conduct your full searches. Evidence can be found in published literature (e.g. peer reviewed journals indexed in electronic databases) and grey literature, that which is not controlled by commercial publishers.


Where should you search?

For undergraduates, published academic literature is usually sufficient for your review. Postgraduates may also need to include what is known as grey literature. This is material that is not controlled by commercial publishers and can be useful for reducing publication bias (papers published in established electronic databases tend to report only positive findings which can pose a threat to the validity of conclusions). See more about searching grey literature below).

Searching published literature

Published academic literature is held in journal databases. The library have already helped you by putting the relevant databases for your discipline in your Databases by Subject page. Select your faculty to see a list of key databases. 

For a systematic review you will require a range of databases to ensure you are not missing any key papers.


Journal article search techniques

Develop a search strategy that will look for the key concepts in your question. This includes deciding and refining your search terms but also initial filtering as appropriate. Help with Planning and saving a search strategy is found in the next section of this guide. 

Consider what limits you will apply (e.g. language/date range) and ensure you use Boolean operators, truncation, etc. as appropriate. Be cautious not to limit too much though and if you do, you need to justify why.

Test your strategy to ensure it finds key papers. If not, examine the subject headings and terminology used in those papers and add to your search strategy.


Grey literature

Grey literature is not controlled by commercial publishers so won't necessarily appear in the journal databases. As mentioned above, including grey literature in your review can help reduce the risk of publication bias.

Examples of grey literature include legislation; government and official documentstechnical or research reports; working papers from groups and committees; dissertations; and conference proceedings. Grey literature can be harder to locate and it is more difficult to apply a systematic search strategy when searching for these.

Searching for grey literature

  • A Google search can be useful for locating a wide range of grey literature in particular reports, papers and official documentation.
  • For theses and dissertations you can use Open Grey and the Networked Digital Library of Theses and Dissertations.
  • Web of Science can be used to identify conference proceedings. 
  • Looking at the references in key papers can be a good way of identifying key journals in the field and then you can specifically search those journals (Journal A‑Z) to identify non-indexed papers and potential papers you may have missed.
  • Contacting key authors in the field directly may help obtain and identify further papers.