FWHM(Hβ_BC) vs. FWHM(C IV_full) and FWHM(Hβ_full) vs. FWHM(C IV_full). Sources are identified according to the different bins of spectral types following colour scheme from Fig. 4. Blue and red open squares represent Pop. A and Pop. B sources from S17 and grey and orange open squares indicate Pop. A and Pop. B from S07, respectively. Horizontal purple line indicates the A-B boundary and the error bars on the top left of the plots refer to 1σ level of confidence for our sample.