1. 1) Zbrozek, J.: Ground Effect on the Lifting Rotor, ARC RM2347, 1950, pp. 1–8.
2. 2) Koo, J. and Oka, T.: Experimental Study on the Ground Effect of a Model Helicopter Rotor in Hovering, NASA TT F-13938, 1971, pp. 1–22.
3. 4) Hayden, J. S.: The Effect of the Ground on Helicopter Hovering Power Required, Proc. AHS 32nd Annual Forum, 1976.
4. 5) Sheridan, P. F. and Wiesner, W.: Aerodynamics of Helicopter Flight near the Ground, Proc. AHS 33rd Annual Forum, 1977.