In medical research, gray literature refers to studies that have been conducted but have not been published in a peer-reviewed medical journal. They may be referenced as conference abstracts or in technical or working papers, giving them a faint but not fully transparent presence in the public domain. Gray literature is typically not easy to search, and it lacks the full accounting of materials, methods, and results required for publication in a peer-reviewed journal. Preprints would also be considered part of gray literature.
