Examples of grey literature that can be valuable to a systematic review include:
- conference abstracts and proceedings
- clinical study reports
- dissertations and theses
- journal preprints
- It expands the reach of a systematic review beyond the scope of the databases mined by a search, increasing the chance of finding pieces of evidence that may be helpful to the final synthesis of data.
- It helps reduce the impact of potential publication bias on the findings of a review.
- It keeps the review current by including upcoming data from recent conferences, doctoral work, and other yet-to-be-published sources.
Ideally, a search of the grey literature should be used in tandem with other forms of hand-searching, including the searching of relevant citations within included articles and of well-known reviews on similar topic.
Where to Find Grey Literature
Below are some resources that list helpful links for exploring the grey literature: