Section Equalities.
Variable elt:Type.
(** Another characterisation of [Equal] *)
(** * Relations between [Equal], [Equiv] and [Equivb]. *)
(** First, [Equal] is [Equiv] with Leibniz on elements. *)

Lemma Equal_Equiv : forall (m m' : t elt),
Equal m m' <-> Equiv Logic.eq m m'.