proposition: Lemma axS (mS : mSystem) (s t u : mS) : mprv ((u ---> s ---> t) ---> (u ---> s) ---> u ---> t).
proof: Proof. exact: axS'. Qed.
imports: mathcomp(all_ssreflect) CompDecModal.libs(edone base fset induced_sym) Setoid Morphisms Relation_Definitions