In 1974, the Library of Congress began to create standardized sets of topical and form subdivisions for use under particular categories of subject headings, or name headings used as subjects. Rather than repeating these subdivisions under all possible headings, only one or a few representative headings from each category are established. Such headings are called pattern headings. The list of pattern headings is not exhaustive, and does not cover every category of knowledge.
Any subdivision used under a heading designated as a pattern heading may also be used under any other heading of the same category if it is appropriate, and if no conflicting heading has been established in the subject authority file.
The pattern headings are listed in three ways:
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