Postage stamps of the United States :
an illustrated description of all United States postage and special service stamps /
United States Postal Service, Office of Special Assistant to the Postmaster General.

APA Citation

United States Postal Service. (1970). Postage stamps of the United States: an illustrated description of all United States postage and special service stamps. Washington: United States Government Printing Office.

MLA Citation

United States Postal Service. Postage Stamps of the United States: an Illustrated Description of All United States Postage And Special Service Stamps. Washington: United States Government Printing Office, 1970.

Warning: These citations may not always be complete (especially for serials).