1. A. V. Apanasenko et al., in Proceedings of the 15th ICRC, Plovdiv, Bulgaria, 1977, Vol. 7, p. 220.
2. V. I. Osedlo et al., in Proceedings of the 27th ICRC, Hamburg, Germany, 2001, Vol. 4, p. 1426.
3. V. I. Galkin et al., Izv. Ross. Akad. Nauk, Ser. Fiz. 66, 1544 (2002).
4. Pamir Collab., Izv. Ross. Akad. Nauk, Ser. Fiz., 55, 650 (1991).
5. V. V. Kopenkin et al., Phys. Rev. D 52, 2766 (1995).