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4. P. W. Milonni:Phys. Lett. A,82, 225 (1981); see alsoAm. J. Phys.,52, 340 (1984) for a more elementary account.
5. This idea was made explicit for the first time byN. S. Kalitsin:JETP (Moscow),25, 407 (1953), and later rediscovered and developed byBraffort and co-workers (6)M. Spighel andC. Tzara:C. R. Acad. Sci.,239, 157 (1954). andMarshali) (7)Proc. R. Soc. London, Ser. A,276, 475 (1963);, among others. A general review on SED can be found in ref. (8) inStochastic Processes Applied to Physics and Other Related Fields, edited byB. Gómez et al. (World Scientific Publ. Co., Singapore, 1983); and shorter, more specific ones in ref. (9-13)T. H. Boyer:Phys. Rev. D,11, 790 (1975).T. A. Brody:Rev. Mex. Fis.,29, 461 (1983).