proposition: Lemma dmAR s t : mprv (~~: (AR s t) <--> EU (~~: s) (~~: t)).
proof: Proof. rewrite /EU. by rule axEI; do ! rewrite -> axDNE. Qed.
imports: mathcomp(all_ssreflect) CompDecModal.libs(edone base fset induced_sym) Setoid Morphisms Relation_Definitions