1. Edward P. Warner, “Aerodynamics,” First Edition, p. 162, McGraw-Hill Book Co., New York and London.
2. Turbulence Factors of N.A.C.A. Wind Tunnels as Determined by Sphere Tests;Platt;National Advisory Committee for Aeronautics Technical Report No. 558,1936
3. Sphere Tests in the N.A.C.A. 8-Foot High Speed Tunnel;Robinson;Journal of the Aeronautical Sciences,1937
4. Leonard B. Loeb, “Kinetic Theory of Gases,” First Edition, p. 20, McGraw-Hill Book Co., New York and London.
5. L. B. Loeb, loc. cit., supra, p. 29.