APA (7th ed.) Citation

United States. Army. Air Corps. (1920). Insignia for observers, Air Service. [publisher not identified].

Chicago Style (17th ed.) Citation

United States. Army. Air Corps. Insignia for Observers, Air Service. Washington: [publisher not identified], 1920.

MLA (9th ed.) Citation

United States. Army. Air Corps. Insignia for Observers, Air Service. [publisher not identified], 1920.

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