proposition: Lemma normalField_normal : 'Gal(E / M) <| 'Gal(E / K).
proof: Proof. by rewrite -normalField_ker ker_normal. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq div) mathcomp(choice fintype tuple finfun bigop ssralg poly) mathcomp(polydiv finset fingroup morphism quotient perm) mathcomp(action zmodp cyclic matrix mxalgebra vector) mathcomp(falgebra fieldext separable)