APA (7th ed.) Citation

United States Postal Service. (1996). Look up a ZIP Code. United States Postal Service.

Chicago Style (17th ed.) Citation

United States Postal Service. Look Up a ZIP Code. Washington, D.C.: United States Postal Service, 1996.

MLA (9th ed.) Citation

United States Postal Service. Look Up a ZIP Code. United States Postal Service, 1996.

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