Skip to Main Content

Copy of Systematic Reviews RD May 24 to consult with Academic Skills: Selecting sources for your literature search

Search strategy design: Selecting sources guidance




"A range of resources are searched where possible: searching only one database is not sufficient for a systematic review as no one database covers all reports of research. The choice of databases is influenced by the research question, but generally, as a minimum for reviews of clinical topics, databases should include MEDLINE, EMBASE and CENTRAL.

The search must seek to identify all relevant reports, including those classed as grey literature (material that is not formally published, such as institutional or technical reports, technology assessments, conference proceedings, or other documents that are not normally subject to editorial control or peer review). Grey literature can be searched using specialised search engines, databases or websites. Additional methods used to identify studies include hand-searching selected journals or conference proceedings, seeking expert opinion, searching the reference lists of included papers or relevant reviews, carrying out citation searches on included studies, and searching clinical trials registers to identify ongoing and recently completed research. Seeking as much available literature as possible minimises the potential for publication bias."

McCool, R., & Glanville, Julie. (2014). What is a systematic review? Evidence Based Health care

Publication bias and systematic reviews

"The search for, and inclusion of, grey literature in a systematic review is an important way to help overcome some of the problems of publication bias"

Hopewell, S., Clarke, M., & Mallett, S. (2005). Grey literature and systematic reviews. Publication bias in meta-analysis: Prevention, assessment and adjustments, 48-72.

Databases for Health Sciences

  • CINAHL   covers nursing and allied health subjects.
  • The Cochrane Library   is a collection of evidence-based medicine databases.
  • Embase  covers pharmacology, medicine and health related subjects. *
  • Medline covers, medicine, nursing, pharmacy and health care. *
  • PubMed covers medicine, nursing, pharmacy and health care as well as life science and biomedical sciences. *
  • Scopus  is multidisciplinary with a strong focus on health related subjects.  
  • PsycINFO  a resource for behavioural and social science research from the American Psychological Association.* 
  • * Research Tips: What's the difference between PubMed, Medline & Embase? A resource from the Library & Information Service at the KEMH, Western Australia.

 Note: this is not an exhaustive list. Consider other databases which may be relevant to your review; to see a full list of databases in Medicine, Nursing & Midwifery and Health Sciences just click on this link

Grey literature and systematic reviews

Mahood Q.Van Eerd D. and Irvin E. (2014), Searching for grey literature for systematic reviews: challenges and benefitsResearch Synthesis Methods5,(3): 221234, doi: 10.1002/jrsm.1106

Haddaway NR, Collins AM, Coughlin D, Kirk S (2015) The Role of Google Scholar in Evidence Reviews and Its Applicability to Grey Literature Searching. PLoS ONE 10(9): e0138237. doi: 10.1371/journal.pone.0138237

Saleh, A. A., Ratajeski, M. A., & Bertolet, M. (2014). Grey literature searching for health sciences systematic reviews: A prospective study of time spent and resources utilized. Evidence Based Library and Information Practice, 9(3), 28-50. DOI:

Selecting databases

Selecting databases for your literature review depends on your review topic. Browse our library guides by Subject to identify the most relevant databases for your discipline. 

Handy tip:

Ulrichsweb, a directory of 300,000 journals, may be useful when selecting databases. You could search for key journals and check the Abstracting/Indexing section to identify databases which include these journals. 

Databases for other disciplines

Grey literature general guidance

“Variously defined as unconventional literature, literature not available via traditional publishing, and publications with little or no general distribution, grey literature represents an immense stash of information that is crucial to various researchers and information professionals.”

Auger, Charles P. Information Sources in Grey Literature. London: Bowker-Saur, 1998.

Searching the grey literature may seem challenging as there are so many sources. You should search the resources that are most relevant to your systematic review.


See also  this free online resource for grey literature searching, compiled by CADTH, the Canadian Agency for Drugs and Technologies in Health: Grey Matters: a practical tool for searching health-related grey literature

For more information on Grey Literature see the next tab in this guide: