intros work ds ni1 ni2 ai a context eq12 mon.
unfold nminimal in |- *.
intros c k k_is_mon k_forces in_a.
apply mon; try assumption.
apply forces_ngamma_eqv with ni2; assumption.
Qed.
(************************************************************************)

Lemma nminimal_shift_work_ds :
forall (i j : Int) (work : nf_list) (ds : disjs) (ni : nested_imps)
(ai : atomic_imps) (a : atoms) (context : flist),
nminimal (NDisj i j :: work) ds ni ai a context ->
nminimal work ((i, j) :: ds) ni ai a context.