Classifying radio emitters from the Sloan Digital Sky Survey - Spectroscopy and diagnosticsM. Vitale, J. Zuther, M. García-Marín, A. Eckart, M. Bremer, M. Valencia-S. and A. ZensusA&A, 546 (2012) A17DOI: https://doi.org/10.1051/0004-6361/201219290