Clusters in the inner spiral arms of M 51: The cluster IMF and the formation history A. Bik, H. J. G. L. M. Lamers, N. Bastian, N. Panagia and M. Romaniello A&A, 397 2 (2003) 473-486 Published online: 17 December 2002 DOI: 10.1051/0004-6361:20021384