Module e_invert := ext_invert e_subst.Module red := ext_red e_invert.Module red_one := ext_red_one e_invert.Module invert := fc_invert wf weak subst.Module unique := fc_unique wf subst.

Lemma open_a_Conv_co : forall a b g, open_tm_wrt_co (a_Conv a g) b = a_Conv (open_tm_wrt_co a b) (open_co_wrt_co g b).