proposition: Lemma Crat_aut nu x : (nu x \in Crat) = (x \in Crat).
proof: Proof. apply/idP/idP=> /CratP[a] => [|->]; last by rewrite fmorph_rat Crat_rat. by rewrite -(fmorph_rat nu) => /fmorph_inj->; apply: Crat_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)