proposition: Lemma gacts_range A : A \subset D -> {acts A, on group R | to}.
proof: Proof. by move=> sAD; split; rewrite ?astabs_range. Qed.
imports: mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat div seq) mathcomp(fintype bigop finset fingroup morphism perm) mathcomp(automorphism quotient)