-lemma fle_flat_sn: ∀I,L,V,T. ⦃L, V⦄ ⊆ ⦃L, ⓕ{I}V.T⦄.
-#I #L #V #T
-elim (frees_total L V) #f1 #Hf1
-elim (frees_total L T) #f2 #Hf2
-elim (sor_isfin_ex f1 f2) /2 width=3 by frees_fwd_isfin/ #f #Hf #_
-/3 width=6 by frees_flat, sor_inv_sle_sn, ex3_2_intro/
+
+/4 width=8 by fle_intro, frees_bind_void, sor_inv_sle_dx, sle_trans/
+qed.
+*)
+lemma fle_flat_dx_sn: ∀L1,L2,V1,V2. ⦃L1, V1⦄ ⊆ ⦃L2, V2⦄ →
+ ∀I,T2. ⦃L1, V1⦄ ⊆ ⦃L2, ⓕ{I}V2.T2⦄.
+#L1 #L2 #V1 #V2 * -L1 #f1 #g1 #L1 #n #Hf1 #Hg1 #HL12 #Hfg1 #I #T2
+elim (frees_total L2 T2) #g2 #Hg2
+elim (sor_isfin_ex g1 g2) /2 width=3 by frees_fwd_isfin/ #g #Hg #_
+/4 width=8 by fle_intro, frees_flat, sor_inv_sle_sn, sle_trans/