Module Type ZGcdProp
(Import A : ZAxiomsSig')
(Import B : ZMulOrderProp A)
(Import C : ZSgnAbsProp A B).
Include NZGcdProp A A B.
(** Results concerning divisibility*)
(** Properties of gcd *)

Lemma gcd_opp_r : forall n m, gcd n (-m) == gcd n m.