United States. War Department. (1931). Infantry and aircraft armament: Browning aircraft machine gun, caliber .50, M1921. GPO.
Chicago Style (17th ed.) CitationUnited States. War Department. Infantry and Aircraft Armament: Browning Aircraft Machine Gun, Caliber .50, M1921. [Washington]: GPO, 1931.
MLA (9th ed.) CitationUnited States. War Department. Infantry and Aircraft Armament: Browning Aircraft Machine Gun, Caliber .50, M1921. GPO, 1931.
Warning: These citations may not always be 100% accurate.