proposition: Lemma join_subG A B G : (A <*> B \subset G) = (A \subset G) && (B \subset G).
proof: Proof. by rewrite gen_subG subUset. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype div path tuple bigop prime finset)