Trends and evolution in the development of grey literature: a review

This paper outlines the principal stages in the development of grey literature (GL), from its first appearance in the post‐war period to its evolution into electronic GL. To this end, the study analyses some of the most important studies and conferences organised up to the 1990s. It also examines the first bibliographies and databases, which transformed the way in which GL was collected and distributed. The second part of the paper briefly outlines the main subjects addressed at international GL conferences, identifying both elements of continuity with earlier work and new developments.