A main heading may be made more specific through the use of one or more types of subdivision, when the heading/subdivision combination appears in the Subject Authority File, or when an appropriate heading can be constructed according to established procedures for using free-floating subdivisions. Subdivisions are also used for the purpose of subarranging large files.

25.0 Reference

25.1 Topical subdivisions

25.2 Form subdivisions

25.3 Geographic subdivisions

25.4 Chronological subdivisions

See also:

A. General Guidelines for Assigning Subject Headings