Gray literature

Definition
Grey literature is

"that information that is both legally and ethically available, but only from specialized channels or through direct local access. It is generally understood as that information whose distribution is not controlled by commercial publishers, and/or that information that is not published, distributed, catalogued or acquired through commercial booksellers and subscription agencies. Grey literature includes working papers, pre-prints, technical reports and technical standards documents, dissertations, data sets, and commercial imagery. Producers of grey literature include: nonprofit and educational organizations; commercial enterprises creating documents for internal use as well as for clients and suppliers; local, state, and national government agencies producing materials for internal use as well as for citizens and vendors, and; a wide variety of informal and formal associations, societies, and clubs. Examples include university yearbooks, yacht club registries, corporate trip reports, and personal notes from public events that are posted to a public bulletin board."