intros.
unfold subst in |- *.
apply typ_sub with e (Ax t) (Ax t :: e); auto with arith pts.
apply typ_wf with d t; auto with arith pts.
Qed.

(* Specifications: *)
Theorem subtype_in_env :
forall (e : env) (t T : term),
typ e t T -> forall f : env, R_in_env ge_type e f -> wf f -> typ f t T.
Theorem subtype_in_env :
forall (e : env) (t T : term),
typ e t T -> forall f : env, R_in_env ge_type e f -> wf f -> typ f t T.