1. L. W. Jones:Proceedings of XII International Cosmic Ray Conference, invited and rapporteur papers (Hobart, 1971), p. 125.
2. A. F. Clark, R. D. Ernst, H. F. Finn, G. F. Griffith, N. E. Hansen andD. E. Smith:Proceedings of the XIII International Cosmic Ray Conference, Vol.3 (Denver, Colo., 1973), p. 2090.
3. W. E. Hazen, A. L. Hodson, D. Winterstein andO. Keller:Proceedings of the XIII International Cosmic Ray Conference, Vol.3 (Denver, Colo., 1973), p. 2087.
4. F. Ashton, D. A. Cooper, A. Parvaresh andA. J. Saleh:Proceedings of the XIII International Cosmic Ray Conference, Vol.3 (Denver, Colo., 1973), p. 2096;J. Phys. A,6, 577 (1973).
5. A. Bohm, W. Diemont, H. Faissner, H. G. Fasold, K. Krisor, K. Maull, Z. Sawaf andH. Umbach:Phys. Rev. Lett.,28, 326 (1970).