μ(v) magnification profiles of the Mg II or Hα lines computed from simultaneously recorded spectra of two images of the quasars of our sample. The μ(v) profiles are shown in red, with the uncertainties in green. The superimposed line profiles from the microlensed image (in blue) and non-microlensed image (in black) were continuum-subtracted, corrected by the M factor, and arbitrarily rescaled. For the Mg II line profiles, the Fe II spectrum was subtracted using the Tsuzuki et al. (2006) template. The zero-velocity corresponds to the Mg IIλ2800 or Hα wavelengths at the source redshift.