1. B em ardini G. Booth E. T. & L indenbaum S. J .
2. Bernardini G. Booth E . T. & Lindenbaum S. J .
3. Brown R . H . Camerini U . Fowler P . H. H eitler H . K ing D. T. & Powell C. F . 1949 P hil. M ag. 40 862.
4. Camerini U . Lock W. O. A m sterd am : N o rth H olland Publishing Company. &■Perkins D. H . 1952 Progress in cosmic ray physics 1 1.