the second edition of The Documentation of the European Communities: A Guide, which contained the first usage of the term "grey literature" in a published work.

The "Luxembourg definition", discussed and approved at the Third International Conference on Grey Literature in 1997, defined grey literature as "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". In 2004, at the Sixth Conference in New York City,