1. G. R. Gruber,Found. Phys. 2, 79 (1972).
2. L. Corsiglia,Scientia 108, 535 (1973).
3. L. Corsiglia,Scientia 108, 863 (1973).
4. L. I. Schiff,Quantum Mechanics, 3rd ed., McGraw-Hill, New York (1968), p. 130.
5. P. Marmier and E. Sheldon,Physics of Nuclei and Particles, Vol. 1, Academic Press, New York and London (1969), pp. 54?56.