1. D. Basu, Sol. Phys. 183, 291 (1998).
2. Ph. Delache, Adv. Space Res. 8, 119 (1988).
3. Surface and Interface of Planets and Satellites, Ed. by A. Dollfus (Academic, London, 1970; Mir, Moscow, 1974).
4. J. A. Eddy and A. A. Boornazian, Bull. Am. Astron. Soc. 11, 437 (1979).
5. R. L. Gilliland, Astrophys. J. 248, 1144 (1981).