intros c work ds ni ai a.
apply In_Work with 0.
apply My_NthO.
Qed.

(* Specifications: *)
Lemma in_ngamma_work_app1 :
forall (bs work : nf_list) (ds : disjs) (ni : nested_imps)
(ai : atomic_imps) (a : atoms) (c : normal_form),
in_ngamma work ds ni ai a c -> in_ngamma (bs ++ work) ds ni ai a c.