Definition lxN := lx N.Definition lx'N := lx' N.

(* Specifications: *)
Lemma Splus_nm : forall n m : nat, S (n + m) = S n + m.
Lemma empty_map_card : forall (A : Set) (m : Map A), (forall x : ad, in_dom _ x m = false) -> MapCard _ m = 0.