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2. Sanger, E., R-Antriebe, Der Deutschen Akademie Der Luftfahrtforschung, Berlin, pp.189-194, 1943.
3. Liepmann, H., and Puckett, A., An Introduction to Aerodynamics of a Compressible Fluid, pp.57and 58;John Wiley and Sons, Inc., New York, 1947.