1. Solar Geophysical Data. ESSA Res. Lab. Boulder (1969–1974).
2. V. V. Belikovich and E. A. Benediktov, Izv. Vyssh. Uchebn. Zaved., Radiofiz.,16, 840 (1973).
3. Observations and Prediction of Solar Activity [Russian translation], Mir, Moscow (1976), p. 291.
4. J. N. Row et al., J. Atm. Terr. Phys.,32, 1609 (1970).
5. S. D. Deshpande and A. P. Mitra, J. Atm. Terr. Phys.,34, 243 (1972).