1. A. N. Tikhonov and V. Ya. Arsenin, Methods for Solving Incorrect Problems [in Russian], Izd. Nauka, Moscow (1974).
2. A. N. Tikhonov, V. V. Vitkevich, V. S. Artyukh, V. B. Glasko, A. V. Goncharskii, and A. G. Yagola, Astron. Zh.,46, No. 3, 472 (1969).
3. A. V. Goncharskii and A. G. Yagola, Dokl. Akad. Nauk SSSR,184, No. 4, 771 (1969).
4. V. A. Putilov and L. M. Risover, in: Research on Geomagnetism, Aeronomy, and Solar Physics [in Russian], No. 36 (1975), p. 169.
5. L. G. Sodin, Izv. Vyssh. Uchebn. Zaved., Fizika, Radiofiz.,14, No. 8, 1143 (1971).