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diff --git a/matita/matita/contribs/lambdadelta/basic_2/i_dynamic/ntas_ntas.ma b/matita/matita/contribs/lambdadelta/basic_2/i_dynamic/ntas_ntas.ma
new file mode 100644
index 000000000..67e7464ca
--- /dev/null
+++ b/matita/matita/contribs/lambdadelta/basic_2/i_dynamic/ntas_ntas.ma
@@ -0,0 +1,27 @@
+(**************************************************************************)
+(*       ___                                                              *)
+(*      ||M||                                                             *)
+(*      ||A||       A project by Andrea Asperti                           *)
+(*      ||T||                                                             *)
+(*      ||I||       Developers:                                           *)
+(*      ||T||         The HELM team.                                      *)
+(*      ||A||         http://helm.cs.unibo.it                             *)
+(*      \   /                                                             *)
+(*       \ /        This file is distributed under the terms of the       *)
+(*        v         GNU General Public License Version 2                  *)
+(*                                                                        *)
+(**************************************************************************)
+
+include "basic_2/i_dynamic/ntas_preserve.ma".
+
+(* ITERATED NATIVE TYPE ASSIGNMENT FOR TERMS ********************************)
+
+(* Main properties **********************************************************)
+
+theorem ntas_trans (h) (a) (G) (L) (T0):
+        ∀n1,T1. ⦃G,L⦄ ⊢ T1 :*[h,a,n1] T0 →
+        ∀n2,T2. ⦃G,L⦄ ⊢ T0 :*[h,a,n2] T2 → ⦃G,L⦄ ⊢ T1 :*[h,a,n1+n2] T2.
+#h #a #G #L #T0 #n1 #T1 * #X1 #HT0 #HT1 #H01 #H11 #n2 #T2 * #X2 #HT2 #_ #H22 #H02
+elim (cnv_cpms_conf … HT0 … H01 … H02) -T0 <minus_O_n <minus_n_O #X0 #H10 #H20
+/3 width=5 by ntas_intro, cpms_trans/
+qed-.