1. Y. S. Kim andL. Voyvodic:Nuovo Cimento,66 B, 183 (1970).
2. M. G. K. Menon andP. V. Ramana-Murthy :Progress in Elementary Particles and Cosmic Rays, Vol.9 (1967).
3. A. W. Wolfendale: Rapporteur’s talkMuons inProceedings of the XI International Conference on Cosmic Rays (Budapest, 1969).
4. L. Bergamasco andP. Picchi:Nuovo Cimento,3 B, 134 (1971).
5. S. Miyake, K. S. Narasimham andP. V. Ramana Murthy:Nuovo Cimento,32, 1905 (1964).