1. Editorial in Pravda (trans. by Brichant, A. L.) (June 4, 1969).
2. Kuiper, G. P., in Atmospheres of the Earth and Planets (edit. by Kuiper, G. P.) (Univ. Chicago Press, 1952).
3. Urey, H. C., Handbuch der Physik, 52, 363 (1959).
4. Mueller, R. F., Icarus, 3, 285 (1964).
5. Rasool, S. I., J. Atmos. Sci., 25, 663 (1968).