Dereddened spectrum of APM 08279+5255 taken at MJD = 52 695 at the 1.82 m Copernico telescope (Asiago, Italy). Superimposed on the spectrum (black solid line), a power-law continuum (blue dot-dashed line), a Gaussian fit of the C IV emission line (green dashed line), and the combination of these two components into a single pseudo-continuum (red solid line) are shown. The dotted line indicates the flux zero level. The major absorption features are denoted with the identifiers used in the text (see Sect. 4) and ticks. The positions of the Lyman limit at λ912 Å in the rest frame and the major emission lines are also indicated.