1. C. F. Powell, P. H. Fowler andD. H. Perkins:The Study of Elementary Particles by the Photographic Method (London, 1959), p. 162.
2. D. R. O. Morrison: CERN/TC/Physics/63-1.
3. G. Cocconi, L. J. Koestler andD. H. Perkins: Lawrence Radiation Laboratory Report No. UCID-1444 (1961), unpublished.
4. J. Orear:Phys. Lett.,13, 190 (1964).
5. P. L. Jain, H. C. Glahe, J. D. Rinaldo andP. D. Bharadwaj:Nuovo Cimento,32, 873 (1964).