Grey literature is “information produced by all levels of government, academics, business and industry in electronic and print formats not controlled by commercial publishing”, (GreyNet) and includes materials such as theses and dissertations, working papers, policy statements, technical reports and government documents.
The Library's subject guides may provide useful links.
Why include grey literature in your review?
For completeness. Whilst it is rarely peer-reviewed, grey literature is often a good source of the most up-to-date information on a topic. Including it reduces publication bias and it may be the only source of some data.
The AACODS checklist is a useful method to quickly evaluate grey literature. Authority Accuracy Coverage Objectivity Date Significance Tyndall, J. AACODS Checklist. Flinders University, 2010.