A method for determining radio continuum spectra and its application to large surveys B. Vollmer, E. Davoust, P. Dubois, F. Genova, F. Ochsenbein and W. van Driel A&A, 431 3 (2005) 1177-1187 Published online: 16 February 2005 DOI: 10.1051/0004-6361:20040562