The Library of Congress Subject Headings is the standard subject heading list for thousands of libraries as well as for a multitude of printed indexes. Near the Reference Desk on top of the Atlas Case are the five "big red books" that have the complete listing of subject headings. Below is a sample page from the Library of Congress Subject Headings for the term "Mental Illness". Click on the areas in RED for definition of the term used by the Library of Congress Subject Headings.