1. 1. Brook, M., 1958: Laboratory studies of charge separation during ice-ice contact. Recent Advances in Atmospheric Electricity, pp. 383-389.
2. 2. Latham, J. and B. J. Mason, 1961: Electric charge transfer associated with temperature gradients in ice. Proc. Roy. Soc., A, 260, 523-536.
3. 3. Yoshida, J., 1944: Charge generation by breaking of ice in thunderstorm. (in Japanese) Teion Kagaku, The Inst. of Low Temperature Science, 1, 149-187.
4. 4. Furth, R., 1942: An elementary theory of thermal diffusion. Proc. Roy. Soc., A, 179, 461-469.
5. 5. Takahashi, T. and C. Magono, 1961: On the crystallization of graupel. (in Japanese) Tenki, Met. Soc. Japan, 8, 154-155.