1. D. D. Millar:Nuovo Cimento,8, 279 (1951).
2. P. Bassi, A. Bianchi eC. Manduchi:Nuovo Cimento,8, 735 (1951);8, 358 (1952).
3. M. W. Bruin:Thesis, Amsterdam (1952). Comunicazione privata.
4. C. Milone:Nuovo Cimento,10, 1126 (1953).
5. N. Arley:On the theory of stochastic processes and their application to the theory of cosmic rays (Copenaghen, 1948), p. 165 e segg.