APA (7th ed.) Citation

United States. Postmaster General. (1930). Change in packing of sheet postal cards. U.S. GPO.

Chicago Style (17th ed.) Citation

United States. Postmaster General. Change in Packing of Sheet Postal Cards. Washington: U.S. GPO, 1930.

MLA (9th ed.) Citation

United States. Postmaster General. Change in Packing of Sheet Postal Cards. U.S. GPO, 1930.

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