GRB 061217: optical observations at calar alto. Jelinek, M. ; Castro-Tirado, A. J. ; Aceituno, J. ; Guijarro, A. ; Monreal, A. ; Alfonso, J. ; de Ugarte Postigo, A. ; Gorosabel, J. Abstract Publication: GRB Coordinates Network Pub Date: 2006 Bibcode: 2006GCN..5933....1J