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3. [English transl.: G. L. Natanson, Soviet Phys.‐Tech. Phys. 4, 1373 (1960)]. This reference also includes a useful set of references.SPTPA30038-5662
4. B. S. Jeffreys, in Quantum Theory I. Elements, edited by D. R. Bates (Academic Press Inc., New York, 1961), p. 244.
5. D. S. Burch, S. J. Smith, and L. M. Branscomb, Phys. Rev. 112, 171 (1958).PHRVAO0031-899X