APA (7th ed.) Citation

United States. Postmaster General. (1925). Air mail service, London to continental Europe. U.S. GPO.

Chicago Style (17th ed.) Citation

United States. Postmaster General. Air Mail Service, London to Continental Europe. Washington: U.S. GPO, 1925.

MLA (9th ed.) Citation

United States. Postmaster General. Air Mail Service, London to Continental Europe. U.S. GPO, 1925.

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