1. Maxwell, J.C.: A treatise on electricity and magnetism, 3rd edn(Oxford University Press 1892),2, art 590
2. Stratton, J.A.: Electromagnetic theory, (McGraw Hill 1941), p. 428 and 475
3. Panovsky, W.H.K., and Phillips, M.: Classical electricity and magnetism, (Addison-Wesley 1962),Chaps. 14 and 19,
4. Schwartz, M.: Principles of electrodynamics, (McGraw-Hill 1972),Chaps. 5 and 6,
5. Marion, J.B.: Classical electromagnetic radiation, (Academic Press 1965),chap. 7,