1. 1. Mason, B. J., 1957: The Physics of Clouds. Oxford University Press, pp. 206-227.
2. 2. Magono, C., K. Higuchi et at.: to be published in the J. Fac. Sci. Hokkaido Univ., Ser. VII.
3. 3. Sapporo Observatory of the Japan Meteorological Agency : to be published.
4. 4. Fujita, T.: private communication.
5. 5. Ishimaru, Y., 1952: Nephology (in Japanese). The Hokuryukan Co., p. 20.