1. V. A. Kuzmin and G. T. Zatsepin, in Proceedings of the 9th International Cosmic Ray Conference, London, 1965, p. 1024.
2. J. N. Bahcall, Phys. Rev. Lett. 13, 332 (1964); Phys. Rev. Lett. 23, 251 (1969).
3. G. V. Domogatsky, Preprint No. 153, FIAN (Lebedev Physical Institute, Moscow, 1969).
4. J. N. Bahcall, Rev. Mod. Phys. 50, 881 (1978).
5. J. K. Rowly, in Proceedings of the Conference on Status and Future of Solar Neutrino Research, Brookhaven National Laboratory (BNL), USA, 1978, p. 265.