The CO(7–6) and [C i](2–1) emission lines (blue color histogram) towards the lensed galaxy HLSJ091828.6+514223. The velocity scale is given relative to z = 5.2429. The red component of the CO(7–6) line is centered at zero velocity. Its blue component is seen at V =  −510 km s^-1. The red and blue components of [C i](2–1) are shifted with respect to CO(7–6) at  − 999.8 km s^-1 owing to their different rest-frame frequencies. Two vertical lines indicate the window used in the bootstrap calculations. The residuals between the original and smoothed data (red color histogram) are shown at the bottom.