CO(4–3) spectra binned in steps of 25 km s^-1 for GN20 (left), 50 km s^-1 for GN20.2a (middle) and GN20.2b (right). The yellow color indicates the velocity ranges where line emission is detected. These regions have been used to derive the integrated fluxes. The red lines show best-fitting double Gaussian profiles to the spectra, and the blue dashed lines show the fits with a single Gaussian. Zero velocities correspond to the redshifts listed in Table 1.