APA (7th ed.) Citation

United States. Postmaster General. (1932). Treatment of air-mail letters prepaid only 5 cents. U.S. GPO.

Chicago Style (17th ed.) Citation

United States. Postmaster General. Treatment of Air-mail Letters Prepaid Only 5 Cents. Washington: U.S. GPO, 1932.

MLA (9th ed.) Citation

United States. Postmaster General. Treatment of Air-mail Letters Prepaid Only 5 Cents. U.S. GPO, 1932.

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