Solar proton events in solar activity cycles 21-24 Bazilevskaya, G. A. ; Logachev, Yu. I. ; Vashenyuk, E. V. ; Daibog, E. I. ; Ishkov, V. N. ; Lazutin, L. L. ; Miroshnichenko, L. I. ; Nazarova, M. N. ; Petrenko, I. E. ; Surova, G. M. ; Yakovchouk, O. S. Abstract Publication: Bulletin of the Russian Academy of Sciences, Physics Pub Date: May 2015 DOI: 10.3103/S1062873815050135 Bibcode: 2015BRASP..79..573B