Catalog of copyright entries.
Part 1, group 2:
Pamphlets, leaflets, contributions to newspapers or periodicals, etc., maps.
APA Citation
Library of Congress. Copyright Office. Catalog of copyright entries. [Washington?]: Library of Congress, Copyright Office.
MLA Citation
Library of Congress. Copyright Office. Catalog of Copyright Entries. [Washington?]: Library of Congress, Copyright Office,
Warning: These citations may not always be complete (especially for serials).