GRB020321 : optical observations. Salamanca, I. ; Rol, E. ; Kaper, L. ; Castro-Tirado, A. J. ; Fruchter, A. ; Greiner, J. ; Hjorth, J. ; Pian, E. ; van den Heuvel, E. Abstract Publication: GRB Coordinates Network Pub Date: 2002 Bibcode: 2002GCN..1385....1S