[O III] line luminosity vs 1.4 GHz radio luminosity of sources classified as HERGs and LERGs, and unclassified PS sources. The red diamonds, orange squares, and blue triangles indicate PS HERGs, PS LERGs and unclassified PS sources, respectively. The [O III] line luminosities vs 1.4 GHz radio luminosities of the sample of HERG and LERG sources presented by Best & Heckman (2012) are plotted as red and black points, respectively. In order to avoid overcrowding of the figure, only 20% of the LERGs in the Best & Heckman (2012) sample are plotted. The solid black line indicates the lower limit to the distribution of HERGs proposed by Best & Heckman (2012).