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Systematic Reviews

Search strategies

Think about your concepts and how they link together ( the position of the term in the column is not relevant).  The concepts in the column Concept 1 are all synonyms for each other as are the terms in Concept 2 and Concept 3.  

Watch the video on Boolean logic to see how you use AND and OR (and NOT)


Concept 1 AND Concept 2 AND Concept 3

Negative-Pressure Ventilation


Positive-Pressure Ventilation


High-Frequency Ventilation




Continous Positive Airway Pressure






Severe acute respiratory syndrome coronavirus 2





Use Boolean Logic to combine your search terms - watch the video


Which databases - eResources


​Before searching consider plotting out your search on a spreadsheet or table in Word, recording where you've searched, when  and the number of results you returned.  You will then have a permanent record of your searches and if the worst happens be able to replicate them.  Most eResources do allow you to save searches if you create an account, but this is a useful back-up. 

You may be able to use a search strategy for another systematic review - but check for quality and it really returns the results you need.

Use the LibGuide for your subject to identify eResources that could be useful for your search.   If your review crosses subject areas use all LibGuides that might be useful.  If in doubt contact your information librarian who has a good knowledge of the resources available and is able to call on colleagues for additional expertise.  

Your information librarian will be able to advise on how to search the individual eResources to get the best results, using all the onboard tools available.

If you have recorded your searches on a spreadsheet you may be able to copy and paste them across eResources, but you may need to "translate" them so they run correctly.  This is particularly true if you are using adjacency searching or truncation.

Google Scholar is a good source, especially for "grey literature" that has not been published in journals. 

eThos - the British Library's database of PhDs is a very useful source of research as you are using the research of others. 

Preprint Services (articles before being formally published)

arXiv - sciences

BiorXiv - biological sciences

MedRxiv - health sciences

NutriXiv - nutritional sciences 

PeerJ life, biology, medicine, and environmental sciences

Preprints  - Multidisciplinary

PsycArXiv  - Psychology

SocArXiv - social sciences

SportRxiv  - Sport

SSRN - social sciences - requires registration.


Bias in your search is almost inevitable for the following reasons. 

  • Positive results more likely to be published than negative
  • Evidence indicates that positive results are likely to be published in English Language 
  • Searching only in one language excludes results in other languages.
  • Be aware of your own unconscious bias and challenge your findings 
  • Contact key researchers to see if they have unpublished results they would be willing to share

When to stop

To be practical therefore most systematic reviewers will create search strategies that are precise enough for them to able to cope with the number of results that are returned.  Your systematic review, even the best, will never uncover everything.