Garrick, I E
naca-report-567
1937
Formulas are given for the propelling or drag force experience in a uniform air stream by an airfoil or an airfoil-aileron combination, oscillating in any of three degrees of freedom; vertical flapping, torsional oscillations about a fixed axis parallel to the span, and angular oscillations of the aileron about a hinge.
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http://naca.central.cranfield.ac.uk/reports/1937/naca-report-567.pdf