Parametric fit of the [OIII] doublet for the QSO2 J0924+01. The left panel shows the line-free regions (in blue) that we selected to fit the underlying continuum (orange solid line). The right panel shows the two kinematic components we fit in the case of this QSO2. The residuals are included in the inset at the bottom. The green shaded region in the residuals corresponds to the region that is affected by atmospheric absorption.