unfold equiv_h in |- *.
intros.
elim H.
elim H0.
intros.
split; apply le_h_trans with g; trivial.
Qed.

(* Specifications: *)
(** ...and symmetric. *)
Lemma equiv_h_sym : forall g h : hedge, equiv_h g h -> equiv_h h g.
unfold equiv_h in |- *.