T_e[O III]-T_e[S III] relation calibrated over CHAOS and G11 selected data, which are reported with different symbols and colour-coded according to their metallicity. The solid dark green line is the MCMC best-fit relation. For comparison, we also report the T_e[O III]-T_e[S III] relations from Rogers et al. (2021) and Méndez-Delgado et al. (2023a), and we see that there is a good agreement, especially at lower temperatures that is the physical region covered by the CHAOS sample. The grey line is the 1:1 line.