How do subject headings work?
The "Library of Congress Subject Headings" is a series of five volumes usually held by large public or academic libraries. These volumes contain a listing of subject terms used by the Library of Congress to catalog books by subject; they also show how the terms are related to one another.
You can ascertain what the appropriate subject headings are for your topic by employing keyword searches (we recommend using the Guided Search) in our online catalog at http://catalog.loc.gov/. If you find books that appear to be relevant to your topic, view the full record for the book in our catalog. The subject headings for that book will be listed there. You can then do subject searches using those headings in the Basic Search Mode. You will get a full list of that subject heading and its subheadings. Often the phrase "more info" appears next to a heading; right click on it for a listing of narrower terms relevant to that subject. A modified online version of "Library of Congress Subject Headings" called "Library of Congress Authorities" is available at http://authorities.loc.gov/. We recommend reading that site's Frequently Asked Questions and Help screens.
More guides and information on Controlled Vocabularies are linked below.