Redshift estimation and comparison with the SDSS meassurements. Upper panel: example of a spectrum from our sample. Vertical lines are the prominent emission lines of our work: Al IIIλ1860, C III]λ1909, and [O II]λ3728. The abscissa scale is rest frame wavelength in Å. The ordinate scale is the normalised flux at 1700 Å. Lower left panel: z_SDSS vs. Δz for the sample. The red point corresponds to the values of Δz and z of the upper panel spectrum. Lower right panel: distribution of Δz. The lime line shows the shift Δz median value: 4.918 × 10⁻⁴ equivalent to ∼65 km s⁻¹.