Parametrisation of the MgII+FeII+FeIII (left) and Hβ+[OIII]+FeII (middle and right panels) of z >  2.5 QSO1 from the sample of Shen (2016). The red lines show the best-fit from multiple systemic, outflow, and broad Gaussian profiles to the line features, together with a two local power laws to the continuum and one (two) template(s) to the FeII features (see text). Each curve with a different colour represent a distinct Gaussian set (or a FeII template) with same kinematic properties, as labeled in the figure. In the right panel we show, for each target, the spectrum around the Hβ+[OIII] lines after the subtraction of the continuum. The red curve represents the best-fit retrieval model from MC fits, and the shaded area encompass 68% of the MC sample; the black curve shows the [OIII] best-fit obtained by Shen (2016). For J2238−0921, we do not detect any [OIII] emission line, consistent with Coatman et al. (2019) and at odds with Shen (2016): the peaks at ∼4900, 5000 and 5150 Å are associated with FeII emission (precisely, the ⁶S iron line group, according to the ordering in Kovačević et al. 2010).