1. Dergachev, V.A., Matveev, G.A., Kruglov, E.M., et al., Izv. Akad. Nauk, Ser. Fiz., 2009, vol. 73, no. 3, p. 437 [Bull. Russ. Acad. Sci. Phys. (Engl. Transl.), 2009, vol. 73, no. 3, p. 419].
2. NOAA (National Oceanic and Atmospheric Administration), Space Weather Prediction Center (SWRS), USA, Boulder, 2010, Available from: http://www.swpc.noaa.gov
3. Crannell, C.J., Frost, K.J., Matzler, C., et al., Astrophys. J., 1978, vol. 223, p. 620.