Reduced millimetre spectra of CVLA958 and CVLA100 observed by the IRAM 30m and ALMA telescopes. The IRAM spectrum for CVLA958 is shown, with its unbinned reduced spectrum presented in blue, and the orange line corresponds to the Gaussian filtered spectrum using a width of 50 km/s (left panel). The CO lines for the redshift solution of z = 3.1755 provided by Birkin et al. (2021) are depicted with the dashed red lines. The applied FTS setups are presented at the top of the plot and are coloured according to the adopted configuration and observing date. The ALMA spectrum for CVLA100 at band 3 is shown in the right panel. The vertical black line corresponds to the possible CO(4-3) emission line at z = 3.29, located at ν = 107.3 GHz. The inset cutout illustrates the velocity-integrated map of the line emission, and the Spitzer 3.6 μm contour (white isocontour) is overlaid.