project reports); describing and advocating for changes to public policy, practice or legislation (white papers, discussion papers, submissions); meeting statutory or other requirements for information sharing or management (annual reports, consultation documents); and many other reasons. Organizations are often looking to create the required output, sharing it with relevant parties quickly and easily, without the delays and restrictions of academic journal and book publishing. Often there is little incentive or justification for organizations or individuals to publish in academic journals and books, and often no need to charge for access to organizational outputs. Indeed, some information organizations may be required to make certain information and documents public. On the other hand, grey literature is not necessarily always free, with some resources, such as market reports, selling for thousands of dollars. However, this is the exception and on the whole grey literature, while costly to produce, is usually made available for free. While production and research quality may be extremely high (with organizational reputation vested in the end product), the producing body, not being a formal publisher, generally lacks the channels for extensive distribution and bibliographic control. Information and research professionals generally draw a distinction between ephemera and grey literature. However, there are certain overlaps between the two media and they undoubtedly share common frustrations such as bibliographic control issues. Unique written documents such as manuscripts and archives, and personal communications, are not usually considered to fall under the heading of grey literature, although they again share some of the same problems of control and access. Impact The relative importance of grey literature is largely dependent on research disciplines and subjects, on methodological approaches, and on the sources they use. In some fields, especially in the life sciences and medical sciences, there has been a traditional preference for only using peer-reviewed academic journals, but studies of methodological quality and reliability have found that "reliability of published research works in several fields may be decreasing with increasing journal rank", contrary to widespread expectations. In other fields, such as agriculture, aeronautics and the engineering sciences in general, grey literature resources tend to predominate. In the last few decades, systematic literature reviews in health and medicine have established the importance of discovering and analyzing grey literature as part of the evidence base and in order to avoid publication bias. Grey literature is particularly important as a means of distributing scientific and technical and public