Ultraviolet resonance multiplets Si IV/S IV] 1402 AA (top), N V 1240 Å (middle) and C IV 1550 Å (bottom) for epoch 1 (left) and epoch 2 (right). The interstellar absorption components are visible on the resonance lines. For comparison the mean wavelength of the blend has been used. Note the strong change in the C IV line at about  + 1300 km s^-1, but note that the C IV and N V are blends with large velocity separation between the components and the variations cannot be uniquely assigned. See text for details.