SDSS DR12 spectra of the 38 BAL QSOs presented here. Top panel: spectrum (blue line) and fit performed in IRAF (orange line); dashed lines indicate the position of the Si IV and C IV peaks as calculated from redshift, and the white area denotes the wavelength interval between 0 and −25 000 km s⁻¹. Bottom panel: residuals between the C IV peak and −25 000 km s⁻¹; absorption below 90% of the continuum is highlighted in orange; the dashed lines indicate the minimum and maximum velocity estimated for the BAL outflow.