APA (7th ed.) Citation

ProQuest (Firm). (1949). Origin of United States Air Mail Service. [publisher not identified].

Chicago Style (17th ed.) Citation

ProQuest (Firm). Origin of United States Air Mail Service. Washington: [publisher not identified], 1949.

MLA (9th ed.) Citation

ProQuest (Firm). Origin of United States Air Mail Service. [publisher not identified], 1949.

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