EWαn2 diagram showing pure SF galaxies according to S06 criterion (blue dots), pure K01 AGN (green squares) and composite SF+AGN objects (black triangles). Classical AGNs as defined by H97 are denoted by open red circles. The dashed vertical line corresponds to S06 separation criterion, the solid one to the H97 boundary, and finally the dashed-dotted line marks the K01 boundary. The error bars in the top right corner correspond to the median errors within our sample of ELG.