1. Aggarwal, M., Jain, R., Mishra, A.P., Kulkarni, P.G., Vyas, C., Sahrma, R., Gupta, M.: 2008, J. Astrophys. Astron. 29, 195.
2. Andriopoulou, M., Mavromichalaki, H., Preka-Papadema, P., Plainaki, C., Belov, A., Eroshenko, E.: 2011, Astrophys. Space Sci. Trans. 7, 439.
3. Aschwanden, M.J.: 2006, Space Sci. Rev. 124, 361.
4. Aschwanden, M.J.: 2012, Space Sci. Rev. 171, 3.
5. Baisultanova, L.M., Belov, A.V., Dorman, L.I., Eroshenko, E.A., Gushchina, R.T., Ishkov, V.N., Yanke, V.G.: 1991, In: Cawley, M., Drury, L.OC., Fegan, D.J., O’Sullivan, D., Porter, N.A., Quenby, J.J., Watson, A.A. (eds.) Int’l. Cosmic Ray. Conf., Dublin 3, 105.