No information provided. No information as to the level of the subject term is provided.

No level specified. The level of the subject term could be determined, but is not specified.

Primary. A subject covers the main focus or subject content of the material.

Secondary. A subject covers a less important aspect of the content of the material.

Undefined. The first indicator is undefined and contains a blank ( ).

Library of Congress subject heading. The formulation of the subject added entry conforms to Library of Congress Subject Headings (LCSH). This includes:

• Topical headings (or topical headings and subdivisions) found in the LC subject authority file or in the latest edition of LCSH, including the latest supplements
• Topical headings found in the LC subject authority file or in the latest edition of LCSH to which is added a free-floating or regular subdivision according to the rules stated in the Subject Cataloging Manual: Subject Headings, particularly subdivisions listed in the pattern lists and geographic subdivisions
• Topical headings not printed in LCSH in the past, but which have been used by LC and which are not likely to have changed (e.g., names of chemical compounds)
• Certain music headings with qualifiers specifying instruments or vocal parts when the main heading has a general scope note printed in LCSH, with or without a general see also reference

Use of value 0 requires that the added entry is appropriate for use in LCSH.

LC subject heading for children's literature. The formulation of the subject added entry conforms to the "AC Subject Headings" section of Library of Congress Subject Headings. Use of value 1 requires that the added entry is appropriate for use in the LC Annotated Card Program.

Medical subject heading. The formulation of the subject added entry conforms to the National Library of Medicine (NLM) authority files. Use of value 2 requires that the added entry is appropriate for use in the NLM authority files.

National Agricultural Library subject authority file. The formulation of the subject added entry conforms to the National Agricultural Library (NAL) subject authority file. Use of value 3 requires that the added entry is appropriate for use in the NAL authority files.

Source not specified. The formulation of the subject added entry conforms to a controlled list, but the source cannot be specified by one of the thesaurus or subject heading systems covered by the other 2nd indicator values or by a code for a specific subject heading list in subfield ǂ2. Use field 653 (Index Term–Uncontrolled) to record terms that are not derived from controlled subject heading lists.

Canadian subject heading. The formulation of the subject added entry conforms to the Canadian Subject Headings. Use of value 5 requires that the added entry is appropriate for use in Canadian Subject Headings.

Répertoire de vedettes-matière. The formulation of the subject added entry conforms to the Répertoire de vedettes-matière maintained by the Bibliothèque de l'Université de Laval. Use of value 6 requires that the added entry is appropriate for use in Répertoire de vedettes-matière.

Source is specified in subfield ǂ2 . Subject headings or terms based on other subject authorities (i.e., on authorities other than those listed here). Identify the source in subfield ǂ2.