1. S. Fukui:Jour. Phys. Soc. Japan,16, 604 (1961).
2. V. A. Dmitriev, G. V. Kulikov, E. I. Massalksh andG. B. Khristiansen:Žurn. Ėksp. Teor. Fiz.,36, 992 (1959);Soviet Physics J.E.T.P.,9, 702 (1959);S. N. Vernov, V. A. Dmitriev, V. I. Solobveva andG. B. Khristiansen:Žurn. Ėksp. Teor. Fiz.,37, 1481 (1959);Soviet Phys. J.E.T.P.,10, 1050 (1959).
3. J. R. Green andJ. R. Barcus:Nuovo Cimento,14, 1356 (1959).
4. J. R. Green andJ. R. Barcus:Nuovo Cimento,21, 361 (1961).
5. K. Greisen:Progress in Cosmic Ray Physics, Vol.3 (Amsterdam, 1956), chap. 1.