NV/CIV vs. FWHM_CIV for the 97 core ERQs in H17. J1714+4148, the four core ERQ from Z16 and the remaining core ERQ in Perrotta et al. (2019) are plotted with the same colour code as in Fig. 1. All other core ERQ from H17 are plotted with small dark red diamonds. The core ERQ are organised into five groups according to the FWHM_CIV range of values, indicated with the vertical dashed lines. The median NV/CIV and FWHM_CIV in km s⁻¹ of the five groups are shown with large orange circles. The error bars correspond to the standard error on the median values for each group. A clear increase with line width is observed in the NV/CIV ratio.