Averaged integrated intensity ratio R(ΔV_i) of the [CI](1−0) emission measured with the Herschel-HIFI and NANTEN2/SMART telescopes as a function of velocity integration interval ΔV_i as explained in the text. The intensity ratios are on average ~2% lower (within the error uncertainties) than unity over the whole range of ΔV_i values, showing that the measured NANTEN2/SMART antenna temperatures are systematically lower than those measured with the Herschel-HIFI telescope by the same amount. The red line delimits the ΔV_i range where the R(ΔV_i) values are closest to unity.