APA (7th ed.) Citation

United States. Post Office Dept. (1936). U.S. foreign air mail routes. Post Office Dept..

Chicago Style (17th ed.) Citation

United States. Post Office Dept. U.S. Foreign Air Mail Routes. [Washington, D.C.]: Post Office Dept., 1936.

MLA (8th ed.) Citation

United States. Post Office Dept. U.S. Foreign Air Mail Routes. Post Office Dept., 1936.

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