Most libraries use Library of Congress Subject Headings (LCSH) to describe the essential contents of books, journals, videos, manuscripts, etc. One handy feature of LCSH is that it subdivides main subject headings by type of information source, for example, Handbooks, Atlases, Encyclopedias, Indexes, Maps, etc.

The most important form subdivisions for finding information sources are in the table below.

Selected LCSH Form Subdivisions