1. F. C. Jones:Phys. Rev. D,6, 2727 (1972).
2. R. G. Cawley:Phys. Rev. D,2, 276 (1970).
3. H. K. Wimmel:Lett. Nuovo Cimento,1, 645 (1971);A. S. Lapedes andK. C. Jacobs:Nature Phys. Sci.,234, 6 (1972);H. K. Wimmel:Nature Phys. Sci.,236, 79 (1972).
4. See,e.g.,A. Sommerfeld:Konik. Akad. Wetensch. Amsterdam Proc.,8, 346 (1904);Lectures in Theoretical Physics, Optics (New York, 1954).
5. See,e.g.,L. D. Landau andE. M. Lifshitz:Electrodynamics of Continuous Media (Oxford, 1960). p. 357.