Spectrum of QSO J 2225+0527 around the C iv emission line. The spectrum has been smoothed by a 21 pixel median filter for clarity (the dark grey line). The lighter grey underlying line indicates the spectrum before smoothing. The two absorption line complexes from C i are marked. The estimated quasar continuum is shown by the dashed line. The conservative uncertainty of 10 per cent is shown by the dotted lines. The vertical labels indicate the strongest emission lines from the quasar.