1. J. Neufeld:Nuovo Cimento,65 B, 33 (1970). Reference to equations in part I will be written in the typical form (I-2.3).
2. J. Neufeld:Phys. Rev.,123, 1 (1961);127, 346 (1962);Journ. Appl. Phys.,34, 2549 (1963).
3. L. Brillouin:Congrès International d’Electricité, Paris, 1932, vol.2 (Paris, 1932), p. 739;Wave Propagation and Group Velocity (New York, 1960); see alsoL. D. Landau andE. M. Lifshitz:Electrodynamics of Continuous Media (Oxford, 1960), p. 254.
4. T. H. Havelock:The Propagation of Disturbances in Dispersive Media (Cambridge, 1914);Th. De Donder:Compt. Rend.,158, 687 (1914).
5. M. Plack:Theory of Electricity and Magnetism (London, 1932), p. 19.