Thesaurus for Graphic Materials
n. (TGM, abbr.)
A controlled vocabulary of subjects, forms, and genres relating to visual materials, intended for use as headings in catalogs and indexes.
Published by the Prints and Photographs Division of the Library of Congress. TGM was originally published as two separate works, LC Thesaurus for Graphic Materials (LCTGM) and Descriptive Terms for Graphic Materials (GMGPC). The works were combined in a single volume in 1995 and are now referred to, respectively, as TGM I and TGM II. Available online at https://www.loc.gov/pictures/collection/tgm/.