1. G. Cooconi, A. N. Diddens, E. Lillkthun andA. M. Wethereli.:Phys. Rev. Lett.,6. 231 (1961).
2. P. Falk-Vairant andG. Valladas:Proceedings Conference on High Energy Physics, (1960), University of Rochester, p. 38.
3. L. Van Hove: private communication; see also ref. (1).
4. A. M. Wetherell:Report Presented at the Conference on Strong Interactions (Berkeley, Calif., Dec, 27–29, 1960),Rev. Mod. Phys. (in press).
5. G. B. Chadwick, G. B. Collins, C. E. Swartz, A. Roberts, S. De Benedktti, N. C. Hien andP. J. Duke:Phys. Rev. Lett.,4, 611 (1933).