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diff --git a/matita/matita/contribs/lambdadelta/static_2/syntax/theq_simple.ma b/matita/matita/contribs/lambdadelta/static_2/syntax/theq_simple.ma
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index 000000000..9ad5ed550
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+++ b/matita/matita/contribs/lambdadelta/static_2/syntax/theq_simple.ma
@@ -0,0 +1,31 @@
+(**************************************************************************)
+(*       ___                                                              *)
+(*      ||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 "static_2/syntax/term_simple.ma".
+include "static_2/syntax/theq.ma".
+
+(* HEAD EQUIVALENCE FOR TERMS ***********************************************)
+
+(* Properies with simple (neutral) terms ************************************)
+
+(* Basic_2A1: was: simple_tsts_repl_dx *)
+lemma simple_theq_repl_dx: ∀h,o,T1,T2. T1 ⩳[h, o] T2 → 𝐒⦃T1⦄ → 𝐒⦃T2⦄.
+#h #o #T1 #T2 * -T1 -T2 //
+#I #V1 #V2 #T1 #T2 #H
+elim (simple_inv_pair … H) -H #J #H destruct //
+qed-.
+
+(* Basic_2A1: was: simple_tsts_repl_sn *)
+lemma simple_theq_repl_sn: ∀h,o,T1,T2. T1 ⩳[h, o] T2 → 𝐒⦃T2⦄ → 𝐒⦃T1⦄.
+/3 width=5 by simple_theq_repl_dx, theq_sym/ qed-.