L_bol inferred from X-ray luminosity vs. L_bol derived from the optical/UV continuum for the sub-sample of QSOs (Shen et al. 2011). Different symbols mark radio classification (see Sect. 4): not classified, light-blue open circles; RL, blue filled circles; detected RI, red filled squares; undetected sources with ℛ^up.lim ∈ (1,10] , yellow open stars; RQ, green filled triangles; out of FIRST, black crosses. The symbol size increases with the redshift (z < 0.7, 0.7 ≤ z < 1.9, and z ≥ 1.9), therefore identifying the continuum wavelength adopted to obtain the bolometric luminosity (see the text). The dotted line marks the one-to-one relation between the luminosities.