1. G. F. Chew andS. C. Frautschi:Phys. Rev. Lett.,7, 394 (1961).
2. K. Igi:Phys. Rev. Lett.,9, 76 (1962);Phys. Rev.,130, 820 (1963).
3. B. Udgaonkar:Phys. Rev. Lett.,8, 144 (1962). The interpretation of theP′ is unclear in this paper due to the neglect of the signature factor.
4. M. G. Olsson: University of Winsconsin preprint (July 1967);
5. Phys. Lett.,26 B, 310 (1968);