VU Systematic Literature Reviews: Databases and other sources of evidence

Sources of evidence 

Systematic reviews are resource-intensive and require a comprehensive, detailed and reproducible search of various sources. The aim of searching multiple databases and employing additional methods is to minimise bias (Cochrane handbook, Ch. 4.2.2) and increase the validity of a systematic review. Hence systematic planning in selecting appropriate databases is mandatory. These electronic databases can be divided into:

  • Bibliographic databases are databases regarded as having relatively comprehensive coverage in specific disciplinary areas.
  • Sources of higher-level evidence include clinical trials and systematic reviews developed by organisations.  
  • Multidisciplinary databases contain a high volume of literature from a broad range of subjects.

Make an appointment with a librarian for help identifying appropriate databases and sources of grey literature. 


​​​​​​The freely accessible online database of biomedical journal citations and abstracts was created by the U.S. National Library of Medicine. More information here

Supplementary search methods

Using traditional electronic databases to search the literature does not always identify all relevant studies. Depending on the topic, one or all of the below methods may be appropriate.

  • Grey Literature: Grey literature includes conference material, working papers, postgraduate dissertations, theses, clinical trial registries, patents, datasets, statistics, government papers and organisational documents. (reports, statements, guidelines, procedures, policies).  Grey literature can be identified by running internet searches and consulting websites of relevant organisations. Here are a few suggestions on where to look.
  • Using Citations: Reviewing the list of references at the end of any key articles is another approach to identify other possible studies. Some databases, such as Web of Science, Scopus and Google Scholar, provide an option to track citations forward and identify papers that have cited a key paper since it was published.
  • Hand Searching: This involves identifying key journals for the topic and manually searching the table of contents or doing a keyword search directly on the journal site. 

The following guides provide more details on searching grey literature:

Victoria University Grey Literature Guide

UniSA Grey Literature and Other Sources Research Guide 

Clinical trial registries

Not all clinical trials end in publications. Clinical Trial Registries help you locate otherwise unpublished or incomplete trials.

More information about trial registries and solving the problems associated with searching them is available through the Medical and health-related trials registers and research registers website managed by Julie Glanville and Carol Lefebvre

PubMed (video)

Network of the National Library of Medicine. (2020, April 23). How PubMed works: Introduction [Video]. YouTube.

PubMed user guide