1. Balthasar, H., Cuveler, G., and Wier, E.: 1987, Solar Phys. 112, 37.
2. Bhatnagar, A., Livingston, W. C., and Harvey, J. W.: 1972, Solar Phys. 27, 80.
3. Gopasyuk, S. I.: 1985, Izv. Krymsk. Astrofiz. Obs. 73, 9.
4. Grigoryev, V. M., Kobanov, N. I., Osak, B. F., Selivanov, V. L., and Stepanov, V. E.: 1985, NASA Conference Publication 2374, p. 231.
5. Kobanov, N. I.: 1983, Solar Phys. 82, 237.