APA (7th ed.) Citation

United States Postal Service. USA philatelic. Stamp Services, United States Postal Service.

Chicago Style (17th ed.) Citation

United States Postal Service. USA Philatelic. Washington, D.C.: Stamp Services, United States Postal Service.

MLA (9th ed.) Citation

United States Postal Service. USA Philatelic. Stamp Services, United States Postal Service.

Warning: These citations may not always be 100% accurate.