Optical monitoring of the blazar ON 231 during CGRO Phases 4 and 5 Nesci, R. ; Tosti, G. ; Villata, M. ; Maesano, M. ; Massaro, E. ; Montagni, F. ; Fiorucci, M. ; Luciani, M. ; Raiteri, C. M. ; de Francesco, G. ; Lanteri, L. ; Chiaberge, M. ; Peila, A. ; Ghisellini, G. Abstract Publication: Cosmic Physics in the Year 2000 Pub Date: June 1997 Bibcode: 1997cpyt.conf...47N