Constraining the rate of GRB visible afterglows with the CFHTLS very wide survey F. Malacrino, J.-L. Atteia, M. Boër, A. Klotz, C. Veillet, J.-C. Cuillandre and the GRB RTAS collaboration A&A, 464 3 (2007) L29-L32 Published online: 29 January 2007 DOI: 10.1051/0004-6361:20066912