The aim of a systematic review it is to find all information available on a particular topic. It is therefore important to widely and thoroughly search published and unpublished research.

There are a number of different sources that can potentially be searched for the literature, including:

• Databases - It is important to search across a range of databases, as no one database covers all the related literature. It is not acceptable to search one database. The decision regarding which databases to search depends on the topic of the review. The searches in the bibliographic databases need to be comprehensive and reproducible.
  To select relevant databases you should:
  • consult the list of databases in this guide
  • check which databases your supervisor recommends
  • ask advice from a librarian
• Grey Literature - This is information not controlled by commercial publishing that is produced by organizations, governments and industry. Searching grey literature as part of a systematic review prevents publication bias.
• Trials - Many clinical trials are unpublished, so when appropriate, it is important to include unpublished and ongoing studies to minimise bias.
• Hand searching - Hand searching (a manual page-by-page examination) journals and conference proceedings may be relevant to your topic as not all trial reports are included in the bibliographic databases. Trials may not also be easily identified in the database search results when screening the titles and abstracts.
• Reference lists - It can be fruitful to search the reference lists of relevant existing systematic reviews and meta-analyses, as well as other key identified studies. Using this search method would be done in the preliminary stages to help determine that search results did contain these papers.

Subject-specific databases

For systematic reviews in the health-related disciplines suggested databases include the following.

Ideas for other relevant databases can be found via LibrarySearch subject categories, or via a relevant subject guide.

Multi-disciplinary databases

Australian-specific databases

The following open access databases include systematic reviews:

What is Grey Literature?

Grey literature is material not commercially or conventionally published. It is produced by government, academics, business, and industry, in both print and electronic formats. Examples include:

• conference papers
• newspaper articles
• reports
• theses
• fact sheets
• research in progress
• government publications
• statistics

See the library guide on Grey literature for more information.

Theses

Determining if a thesis has already been completed that is closely related to your topic is recommended.

Conferences

Conference papers can be published in books, journal articles or abstracts, and many organisations make them available online.

You can refine your search by publication or document type when searching many library databases. Use Google or Google Scholar to search for the name of the conference or organisation.

Government sources

Repositories

Tools and Directories

Trials Register Databases

News articles

Systematic reviews may be published in the peer-reviewed journal literature. You can find these reviews using databases and restricting your search to publication type 'systematic review'.

Systematic reviews are also produced by government, NGOs, agencies and academic institutions and made available on websites. These reviews are an example of 'unpublished' (or 'grey') research. To find these reviews, you need to:

• check the websites of relevant organisations
• or, using Google Advanced Search, enter search terms for your topic in the top search box ('all these terms') as well as the phrase 'systematic review'. 

Major producers of systematic reviews