1. Akasofu, S.-I.: 1981, Solar Phys. 71, 107
2. Babin, A. N.: 1980, Izv. Krym. Astrofiz. Obs. 62, 142
3. Bogod, V. M. and Gelfreikh, G. B.: 1980, Solar Phys. 67, 29
4. Brown, J. C., Smith, D. F., and Spicer, D. S.: 1981, in S. Jordan (ed.), The Sun as a Star, NASA SP-450, p. 413
5. Cheng, C.-C., Bruner, E. C., Jr., Tandberg-Hanssen, E., Woodgate, B. E., Shine, R. A., Kenny, P. J., Henze, W., and Poletto, G.: 1982, Astrophys. J. 253, 353