APA (7th ed.) Citation

United States. Postmaster General. (1927). Information regarding 1st and 2nd class post offices. U.S. GPO.

Chicago Style (17th ed.) Citation

United States. Postmaster General. Information Regarding 1st and 2nd Class Post Offices. Washington: U.S. GPO, 1927.

MLA (9th ed.) Citation

United States. Postmaster General. Information Regarding 1st and 2nd Class Post Offices. U.S. GPO, 1927.

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