Top panel: [O III]λ5007 total luminosity as obtained by our spectral analysis vs. redshift for the 624 candidate AGNs coloured by nominal SDSS S/N, as labelled in the colour bar. Circles, stars, triangles, and squares refer to Georgakakis & Nandra (2011), Jin et al. (2012), Wu et al. (2012), Trichas et al. (2013) subsamples, respectively, used to construct our X-ray/SDSS sample. Bottom panel: absorption corrected X-ray luminosity vs. redshift for the same sample of targets, distinguishing between the different subsamples, as labelled in the figure.