Comparison between our mass-weighted metallicities (in the case of BC03 models) and the values reported in the literature. In particular, coloured filled circles (colour-coded as in Fig. 10) are our results (the cyan curve is a second order fit to our data); the grey curve is the scaling relation provided by Thomas et al. (2010), with its dispersion (grey shaded region), while black open circles and vertical bars are the measures (and dispersions) performed on our sample by Gallazzi et al. (2005). The light-brown curve is the relation derived by McDermid et al. (2015), together with its dispersion (light-brown shaded region).