APA (7th ed.) Citation

United States. Postmaster General. (1929). Return card on air mail. U.S. GPO.

Chicago Style (17th ed.) Citation

United States. Postmaster General. Return Card on Air Mail. Washington: U.S. GPO, 1929.

MLA (9th ed.) Citation

United States. Postmaster General. Return Card on Air Mail. U.S. GPO, 1929.

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