Upper panel: predictions on [O/Fe] versus [Fe/H] from Models 1 and 2 [short-dashed (red) and solid (black) lines, respectively] are compared one to another and with data from the forbidden [O i] lines (see Fig. 8 caption for references). Lower panel: same as the upper panel, but for Models 6 and 7 [dot-dashed and solid (black) lines, respectively]. See the electronic edition of the journal for a colour version of this figure.