Cita APA (7a ed.)
United States Postal Service. The Postal Service Guide to U.S. Stamps: Updated Stamp Values (Vigésima octava edición.).
Cita Chicago Style (17a ed.)
United States Postal Service. The Postal Service Guide to U.S. Stamps: Updated Stamp Values. Vigésima octava edición.
Cita MLA (9a ed.)
United States Postal Service. The Postal Service Guide to U.S. Stamps: Updated Stamp Values. Vigésima octava edición.
警告：這些引文格式不一定是100％准確.