The REW_C IV vs. v_C․IV relation compared with the 0.05, 0.1, 0.3, 0.5, 0.68, 0.9 and 0.99 contour levels (relative to the peak) of the SDSS DR7 sample (Shen et al. 2011; Vietri et al. 2018) and with the values from Schindler et al. 2020 (grey points). For simplicity, we plot here the mean values derived using all the available values reported in Table 3. We note that the fit takes into account all the existing values of v_C․IV and REW_C IV(see Section 3.2).