Grey literature is generally considered to be material published or made available by organisations or individuals, not through commercial publishers. This can include: clinical study reports, conference abstracts, government documents, organisational reports, personal communication, pre-prints, regulatory documents, study registrations, social media posts and theses.
Searching for grey literature can be problematic, as it isn't collected, organised or stored in a consistent way. You will need to be flexible in your approach, depending on the type of grey literature you need – this will differ from review to review.
Here are a few suggestions on where to look. Please also contact your outreach librarian or subject librarian for advice related to your review.
Reporting your grey literature search is not as straightforward as reporting a search on a bibliographic database. You should aim to record the following information: