intros i b work ds ni bs ai ai' a context notlookup equiv_ins mon.
unfold nminimal in |- *.
intros c k k_is_mon k_forces_ngamma in_a.
apply mon; try assumption.
apply forces_ngamma_shift_ai_work_old with bs ai'; assumption.
Qed.

(* Specifications: *)
Lemma nminimal_shift_work_a :
forall (i : Int) (work : nf_list) (ds : disjs) (ni : nested_imps)
(ai : atomic_imps) (a a' : atoms) (context : flist),
EQUIV_INS unit i (fun _ : unit => tt) tt a a' ->
nminimal (NAtom i :: work) ds ni ai a context ->
nminimal work ds ni ai a' context.