SFR surface density as function of gas-mass surface density for a sample of local and high-redshift galaxies, including HZ10, LBG-1, AzTEC-3, and CRLE, adapted from Pavesi et al. (2019) and Shi et al. (2011). Our objects, GELDAs, and non-GELDAs are very dense, and all of them are found slightly below other objects, which might be related to the very high gas density in these objects where the turbulence can produce a negative effect on the SFE, which is thus lower than in other high-redshift galaxies at the same gas surface density. From bottom to top, the shaded areas correspond to low-surface-brightess (magenta), late-type (blue), early type (green), hi-z star-forming (yellow), and hi-z sub-millimetre (red) galaxies. They are also given inside the figure.