Correlation between the X-ray luminosity L_{cat, 0.5−2} based on the flux given in the 3XMM-DR5 catalogue and the X-ray bolometric luminosity L₅₀₀ derived by Takey et al. (2013, 2014) for the 25 common clusters. The solid line represents the best fit of the relation (BCES orthogonal regression, Python module) based on 21 systems (green dots) after excluding four systems (blue open circles), see the text for more detail. The best-fit parameters are written in the lower right corner.