proposition: Lemma aut_Crat nu : {in Crat, nu =1 id}.
proof: Proof. by move=> _ /CratP[a ->]; apply: fmorph_rat. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun ssrnat eqtype seq choice) mathcomp(div fintype path bigop finset prime order ssralg) mathcomp(poly polydiv mxpoly generic_quotient countalg) mathcomp(ssrnum closed_field ssrint archimedean rat intdiv) mathcomp(algebraics_fundamentals)