APA (7th ed.) Citation

United States. Postmaster General. (1928). Name and address of sender and legible postmark must be placed on 4th-class mail. U.S. GPO.

Chicago Style (17th ed.) Citation

United States. Postmaster General. Name and Address of Sender and Legible Postmark Must Be Placed on 4th-class Mail. Washington: U.S. GPO, 1928.

MLA (9th ed.) Citation

United States. Postmaster General. Name and Address of Sender and Legible Postmark Must Be Placed on 4th-class Mail. U.S. GPO, 1928.