581 Subfield $a - Publications about described materials note:

Subfield $a contains the citation or information about a publication that is a study or analysis of the described materials.

Examples:

581 ##$aLevine, Lawrence W. "William Shakespeare and the American People: A Study in Cultural Transformation." American Historical Review, 89 (February 1984).

581 ##$aConverse, Philip E., Aage R. Clausen, and Warren E. Miller. "Electoral Myth and Reality: the 1964 Election." American Political Science Review, 59 (June 1965).

581 8#$aThe adjusted 1970 numbers are used as a basis for the annual county population estimates published in Current Population Reports Series P-26 and P-25.

581 8#$aReproduction: Antiques, June 1952, p. 76.

581 8#$aInventory of American Sculpture: photocopy. 1982.