Relation between T[O III] and T[O II] for the MARTA sample (gold hexagons), compared with various samples from the literature at low (grey dots) and high redshifts (from JWST archival data, orange triangles). The plot also shows the 1:1 relation (dashed blue line) and two empirical calibrations of the T₂ − T₃ relation, from Pilyugin et al. (2009, dashed purple line) and Garnett (1992, dashed magenta line). The red squares represent the median values of the entire sample, binned in T₃, with uncertainties given by the standard deviation within each bin. The red line shows the best-fit relation derived in this work.