1. J. C. Maxwell,A Treatise on Electricity and Magnetism(Clarendon, Oxford, 1873), Vol.I, Secs. 713, 714, and 715.
2. D. Lorrain and D. R. Corson,Electromagnetism(Freeman, San Francisco,1979), Chap. 8, problems 8-5E and 8-6E; Chap. 9, Secs. 9.1.3, 9.1.4, and 9.1.5.
3. J. D. Kraus,Electromagnetics, 2nd ed. (McGraw–Hill, New York, 1973), Chap. 4.
4. P. M. Fishbane, S. Gasiorowicz, and S. T. Thornton,Physics for Scientists and Engineers, 2nd ed. (Prentice Hall, New York, 1996), Chap. 30.
5. L. W. McKeehen, Rev. Sci. Instrum.7, 150 (1936).