[El/Fe] versus metallicity and age. In the left panels, we show [Fe/H] versus [El/Fe], and in the right panels we show age versus [El/Fe] for our sample of OCs divided into the three galactocentric regions. In blue, we show the OCs located in the inner disc, in green we show those located in the solar neighbourhood, and in pink we show the ones located in the outer disc. In the right panels, the continuous lines are the univariate linear regressions (one for each radial region, colour-coded according to the corresponding sample of OCs), while the shaded regions are their confidence intervals.