Classifying radio emitters from the Sloan Digital Sky Survey - Spectroscopy and diagnostics M. Vitale, J. Zuther, M. García-Marín, A. Eckart, M. Bremer, M. Valencia-S. and A. Zensus A&A, 546 (2012) A17 Published online: 01 October 2012 DOI: 10.1051/0004-6361/201219290