Time variations in the cosmic ray electron spectrum above 500 MeV Bleeker, J. A. M. ; Burger, J. J. ; Deerenberg, A. J. M. ; van de Hulst, H. C. ; Scheepmaker, A. ; Swanenburg, B. N. ; Tanaka, Y. Abstract Publication: International Cosmic Ray Conference Pub Date: 1970 Bibcode: 1970ICRC....1..209B