The term refers to materials and research produced by organizations such as academic departments and centres, think tanks and other non-governmental organizations, corporations, and other stakeholders. Grey literature take many forms and they may be referred to as reports (technical, research, etc.), working papers, white papers, project evaluation documents, and so on. They are usually distributed outside of the normal publishing and distribution channels and can be hard to find. They are, however, valuable resources when researching public policy and many of them can be found using the tools listed here.