SDSSJ005700.18+143737.7. Top panels: Details are the same as in Fig. A.1. (c) Continuum-normalised UV spectrum from SDSS DR-16 with adopted continuum marked in colour. Bottom panels: Fits for (d) Si IVλ1397+O IV]λ1402, (e) C IVλ1549+He IIλ1640, and (f) the 1900 Å blend. Pink dashed lines show the final fitting. Broad components are represented by black lines, while blueshifted components are in blue. Green line represents the additional Fe IIIλ1914 line in the red side of C III], observed in extreme Pop. A sources. Brown lines represent the absorptions seen in the spectrum and modelled as negative-flux Gaussians.