1. M. M. Block, W. M. Fairbank, E. M. Harth, T. Kikuchi, C. M. Meltzer andJ. Leitner:Proc. Intern. Conference on High Energy Accelerators and Instrumentation (CERN, 1959), p. 461.
2. H. Primakoff:Rev. Mod. Phys.,31, 802 (1959).
3. H. L. Anderson H. L. Anderson, E. P. Hincks, C. S. Johnson, C. Rey andA. M. Segar: Communication at the Aix-en-Provence International Conference on Elementary Particles (September, 1961).
4. M. Schiff, R. Hildebrand andC. Giese:Phys. Rev.,122, 265 (1961).
5. P. Ammiraju andL. M. Lederman:Nuovo Cimento,4, 283 (1956).