Grey literature refers to literature which has not been formally/commercially published. This is particularly useful for systematic reviews as it can identify literature which is outside 'publication bias'. This is when the outcome of an experiment or research study influences the decision whether to publish it or not - so studies with a positive outcome are more likely to be published than those which show little or no positive effect for a treatment.
Grey literature includes academic papers, including theses and dissertations, research and committee reports, government reports, conference papers, and ongoing research. There is no single database that covers all types of grey literature, so you will need to consider what types of grey literature are most relevant to your review. You should also keep a record of which sites you have searched and how you have searched them, so that this can be reported.
Useful sources for grey literature include the following:
Searchable index and access to open access research theses from European universities.
This link opens in a new windowSearchable index of UK theses with full text available to order.
The most comprehensive collection of dissertations and theses from around the world, spanning from 1743 to the present day and offering full text for graduate works added since 1997, along with selected full text for works written prior to 1997. It contains a significant amount of new international dissertations and theses both in citations and in full text.
If you wish to access full text theses, please make sure the "Full text" option is ticked under the search bar.
