APA (7th ed.) Citation

United States. National Advisory Committee for Aeronautics. (1937). Helicopter problems. [s.n.].

Chicago Style (17th ed.) Citation

United States. National Advisory Committee for Aeronautics. Helicopter Problems. [Washington]: [s.n.], 1937.

MLA (9th ed.) Citation

United States. National Advisory Committee for Aeronautics. Helicopter Problems. [s.n.], 1937.

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