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diff --git a/matita/matita/contribs/lambda_delta/basic_2/grammar/tstc_tstc.ma b/matita/matita/contribs/lambda_delta/basic_2/grammar/tstc_tstc.ma
new file mode 100644
index 000000000..a32d045b5
--- /dev/null
+++ b/matita/matita/contribs/lambda_delta/basic_2/grammar/tstc_tstc.ma
@@ -0,0 +1,32 @@
+(**************************************************************************)
+(*       ___                                                              *)
+(*      ||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/grammar/tstc.ma".
+
+(* SAME TOP TERM CONSTRUCTOR ************************************************)
+
+(* Main properties **********************************************************)
+
+(* Basic_1: was: iso_trans *)
+theorem tstc_trans: ∀T1,T. T1 ≃ T → ∀T2. T ≃ T2 → T1 ≃ T2.
+#T1 #T * -T1 -T //
+#I #V1 #V #T1 #T #X #H
+elim (tstc_inv_pair1 … H) -H #V2 #T2 #H destruct //
+qed.
+
+theorem tstc_canc_sn: ∀T,T1. T ≃ T1 → ∀T2. T ≃ T2 → T1 ≃ T2.
+/3 width=3/ qed.
+
+theorem tstc_canc_dx: ∀T1,T. T1 ≃ T → ∀T2. T2 ≃ T → T1 ≃ T2.
+/3 width=3/ qed.