M_BH(Hβ) compared to M_BH(C IV), (left panel) and to M_BH(Al III), (right panel). Open squares on the left plot represent the low- and high-redshift sources analysed by Marziani et al. (2019; blue and red for high-z and grey and orange for low-z Pop. A and Pop. B, respectively). Blue dots on the right panel are for the M22 data. Green and purple dashed lines indicate the linear regressions using bisector and orthogonal methods, respectively. Colour scheme is the same as in Fig. 4.