proposition: Lemma normal_Econv_NF_conv : forall T T' : term, Econv T T' -> normal T -> normal T' -> NF_Econv T T'.
proof: Proof. intros T T' H. elim Econv_church_rosser with T T'; auto with ecoc; intros. apply trans_NF_Econv_NF_Econv with x; eauto with ecoc. Qed.
imports: Termes Conv Ered Types ETypes Conv_Dec Strong_Norm