1. J. W. Elbert, T. K. Gaisser andT. Stanev:Phys. Rev. D,27, 1448 (1983).
2. L. V. Volkova:Proceedings of the International Conference on Cosmic Rays, Vol.7 (Bangalore, 1983, p. 22;L. V. Volkova andG. T. Zatsepin:Sov. J. Nucl. Phys.,37, 212 (1983).
3. H. Inazawa andK. Kobayakawa:Prog. Theor. Phys.,69, 1195 (1983).
4. H. Inazawa,K. Kobayakawa andK. Kitamura:Proceedings of the International Conference on Cosmic Rays, Vol.11 (Bangalore, 1983), p. 439.
5. C. Castagnoli, P. Piccini, A. Castellina, B. D’Ettorre Piazzoli, G. Mannocchi andS. Vernetto:Nuovo Cimento A,82, 78 (1984).