APA (7th ed.) Citation

United States. Post Office Department. (1940). United States Official Postal Guide, Monthly Supplement to Parts I and II; May 1940. [s.n.].

Chicago Style (17th ed.) Citation

United States. Post Office Department. United States Official Postal Guide, Monthly Supplement to Parts I and II; May 1940. [Washington]: [s.n.], 1940.

MLA (9th ed.) Citation

United States. Post Office Department. United States Official Postal Guide, Monthly Supplement to Parts I and II; May 1940. [s.n.], 1940.

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