1. V. G. Kirillov-Ugryumov, Vestn. Akad. Nauk SSSR,9, 12 (1981).
2. C. E. Fichtel, Proc. Inter. Workshop on VHE Gamma-Ray Astronomy, Ootacamund (1981), p. 118.
3. J. F. Ormes, M. H. Israel, R. Mewald, and M. Wiendenbeck, 20th ICRC, Moscow,2, 378 (1987).
4. K. E. Turner, 19th ICRC, La Jolla,9, 399 (1985).
5. R. J. Protheroe, 20th ICRC, Moscow,8, 21 (1987).