1. R. P. Feynmann, R. B. Leighton, and M. Sands: Lectures in Physics ,Addison-Wesley, New York (1964).
2. W. F. Gauster, D. C. Freemann, and H. M. Long, Proc. World Power Conf. Paper 56, p. 1954 (1964).
3. P. A. Klaud: Austrian Patent. 256, 956, Nov. 11 (1967).
4. G. Bogner and F. Schmid: Naturwissenschaften 57:414 (1970); Elektrotechische Zeitschrift A 92:740(1971).
5. G. Aschermann, E. Friederich, E. Justi, and J. Kramer: Phys. Z. 42:(21/22): 349–360 (1941).