Upper panel: spectra of images A (top) and B (bottom) of J0818+0601. To enhance visibility, the spectra have been divided by an approximate continuum identical for images A and B, and the spectrum of image B has been multiplied by a factor 2. The spectra are given in arbitrary units. Green and magenta tick marks on the top indicate intrinsic absorption features at redshift z = 2.323 (C IVλλ1548.203,1550.777; Si IVλλ1393.755,1402.770; N Vλλ1238.821,1242.804; Lyαλ 1215.670) and z = 2.302 (C IV; N V), respectively. Red tick marks in the middle indicate intervening absorption lines at redshift z = 1.0065 identified in both images A and B (Table 1). Lower panel: A/B flux density ratio. Tick marks indicate the same features as in the upper panel.