GRB 020531, simultaneous optical observations. Castro-Tirado, A. J. ; Castro Cerón, J. M. ; de Ugarte Postigo, A. ; Hudec, R. ; Jelinek, M. ; Bernas, M. ; Pata, P. ; Berna, J. A. Abstract Publication: GRB Coordinates Network Pub Date: 2002 Bibcode: 2002GCN..1430....1C