1. See, for example, B. I. Cohen, A. N. Kaufman, and K. M. Watson, Phys. Rev. Lett.
29, 581 (1972).
2. See, for example, M. Coreli, Representations of the Rotation and the Lorentz Groups, Dekker, New York (1976).
3. E. S. Sarachik and G. T. Schappert, Phys. Rev. D
1, 2738 (1970).
4. See, for example, A. Yariv, Optical Electronics, 3rd ed., Holt, Rinehart, and Winston, New York (1985).
5. A general discussion of the eikonal method for a general wave equation has been given by S. Weinberg, Phys. Rev.
126, 1899 (1962). In particular, see Section IV of that paper for a derivation of the path integral in (6.3.7).