Examples of FeLoBAL QSOs. The red solid vertical lines indicate the positions of the emission lines that are typical for QSO spectra; the blue dotted lines mark the positions of typical absorption lines. The best estimates for the emission line redshift z and the absorption line redshift z_abs are given at the top of each panel. The vertical green dotted line marks the position of the Ly α line for the redshift given by the SDSS DR16. The flux is in units of 10⁻¹⁷ erg s⁻¹ cm⁻² Å⁻¹. The spectrum of SDSS J090132.30+252400.6 (bottom right) is the result of the coaddition of three SDSS spectra.