proposition: Lemma actsI : [acts A, on S :&: T | to].
proof: Proof. by apply: subset_trans (astabsI S T); rewrite subsetI AactS. Qed.
imports: mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat div seq) mathcomp(fintype bigop finset fingroup morphism perm) mathcomp(automorphism quotient)