proposition: Lemma braid_ltrans : left_transitive braidcongr.
proof: Proof. Proof using. by have:= braid_equiv; rewrite equivalence_relP => [] [Hrefl Hltr]. Qed.
imports: HB(structures) mathcomp(all_ssreflect) mathcomp(fingroup perm morphism presentation) mathcomp(ssralg poly ssrint) permcomp tools permuted combclass congr