Propellers. Calculation of induced efficiency of heavily loaded propellers having infinite number of blades [with list of references], by F. Lösch: Induced efficiency of optimum propellers having finite number of blades [with list of references], by K. N. Kramer: Prospects of propeller drive for high flying speeds [with list of references], by G. Bock and R. Nikodemus; [translation by J. Vanier from] Luftfahrtforschung, v. 15, no. 7, July 6, 1938.