1. Antinucci M., Bertin A., Capiluppi P., Bruno M. D., Rossi A. M., Vannini G., Giacomelli G., Bussiere A., Lett. Nuovo Cimento6 (1973), 121.
2. Dau W. D., Carstensen K., Jokisch H., Proc. 14th Int. Conf. on Cosmic Rays (Munich)6 (1975), 1931.
3. Bandyopadhyay P., Bhattacharyya S., Lett. Nuovo Cimento17 (1976), 399; Nuovo CimentoA XX (1978), in press.
4. Erlykin A. D., Ng L. K., Wolfendale A. W., Journ. Phys.A 7 (1974), 2059.
5. Baradzei L. T.,Rubtsov V. I.,Smorodin Y. A.,Solovyov M. V.,Tolkachev B. V., Proc. Int. Conf. on Cosmic Rays and Earth Storm, Kyoto 1961; Journ. Phys. Soc. Japan, Suppl. A III17 (1962), 433.