1. Björnsson, S. (personal communication).
2. Langmuir, I., Proc. Amer. Phil. Soc., 97, 167 (1948).
3. Burdecki, F., Weather, 19, 113 (1964).
4. deBary, E., and Bullrich, R., Met. Rdsch., Berlin, 12, 89 (1959).
5. Watson, K., Murray, B. C., and Brown, H., J. Geophys. Res., 66, 3033 (1961).