1. Trivelpiece, Gould, Cooper, “Electromechanical modes in plasma waveguides and their application to measurement of electron density in a cylindrical plasma column,” ONR Tech. Memo. Nonr 220 (13), March, 1958.
2. See J. A. Stratton,Electromagnetic Theory(McGraw-Hill Book Company Inc., New York, 1941), pp. 355, 371, 565.