United States. National Advisory Committee for Aeronautics. (1939). Wind-tunnel investigation of N. A. C. A. 23021 airfoil with two arrangements of 40-percent-chord slotted flap. [s.n.].
Chicago Style (17th ed.) CitationUnited States. National Advisory Committee for Aeronautics. Wind-tunnel Investigation of N. A. C. A. 23021 Airfoil with Two Arrangements of 40-percent-chord Slotted Flap. [Washington]: [s.n.], 1939.
MLA (9th ed.) CitationUnited States. National Advisory Committee for Aeronautics. Wind-tunnel Investigation of N. A. C. A. 23021 Airfoil with Two Arrangements of 40-percent-chord Slotted Flap. [s.n.], 1939.
Warning: These citations may not always be 100% accurate.