proposition: Lemma astabC A S : (A \subset 'C(S | to)) = (S \subset 'Fix_to(A)).
proof: Proof. by rewrite astabCin ?subsetT. Qed.
imports: mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat div seq) mathcomp(fintype bigop finset fingroup morphism perm) mathcomp(automorphism quotient)