proposition: Lemma cfextprodNr g h : g \ox - h = - (g \ox h).
proof: Proof. Proof using. by rewrite linearN. Qed.
imports: HB(structures) mathcomp(all_ssreflect) mathcomp(ssralg fingroup morphism perm gproduct) mathcomp(ssrnum matrix vector mxalgebra algC) mathcomp(classfun character mxrepresentation) tools ordcast partition sorted permcomp cycles cycletype permcent