Grey literature is "that which is produced on all levels of government, academics, business and industry in print and electronic formats, but which is not controlled by commercial publishers," according to the Luxembourg Convention.
This category includes reports, memoranda, conference proceedings, standards, technical documentation, and government documents.
NLM recognizes the impossibility of collecting all of the grey literature with potential relevance to health. The Library's collecting intent is to collect a wide range of works representing diverse cultural and political perspectives. The collecting effort is particularly strong in health services research, health policy and economics, toxicology, and public health. Emphasis is on the publications of major national and international associations, institutes, and agencies. Publications of other organizations (such as regional, state and local associations) are collected more selectively, with emphasis on publications of broad interest to U.S. health professionals, those representing unique viewpoints, and others likely to be of historical interest.