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diff --git a/matita/matita/contribs/lambdadelta/apps_2/examples/ex_cnv_eta.ma b/matita/matita/contribs/lambdadelta/apps_2/examples/ex_cnv_eta.ma
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+(**************************************************************************)
+(*       ___                                                              *)
+(*      ||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/rt_computation/cpms_drops.ma".
+include "basic_2/dynamic/cnv.ma".
+
+(* EXAMPLES *****************************************************************)
+
+(* Extended validy (basic?_2) vs. restricted validity (basic_1) *************)
+
+(* Note: extended validity of a closure, height of cnv_appl > 1 *)
+lemma cnv_extended (h) (p): ∀G,L,s. ⦃G, L.ⓛ⋆s.ⓛⓛ{p}⋆s.⋆s.ⓛ#0⦄ ⊢ ⓐ#2.#0 ![Ⓕ,h].
+#h #p #G #L #s
+@(cnv_appl … 2 p … (⋆s) … (⋆s))
+[ #H destruct
+| /4 width=1 by cnv_sort, cnv_zero, cnv_lref/
+| /4 width=1 by cnv_bind, cnv_zero/
+| /5 width=3 by cpm_cpms, cpm_lref, cpm_ell, lifts_sort/
+| /5 width=5 by cpm_cpms, cpm_bind, cpm_ell, lifts_uni, lifts_sort, lifts_bind/
+]
+qed.
+
+(* Note: restricted validity of the η-expanded closure, height of cnv_appl = 1 **)
+lemma vnv_restricted (h) (p): ∀G,L,s. ⦃G, L.ⓛ⋆s.ⓛⓛ{p}⋆s.⋆s.ⓛⓛ{p}⋆s.ⓐ#0.#1⦄ ⊢ ⓐ#2.#0 ![Ⓣ,h].
+#h #p #G #L #s
+@(cnv_appl … 1 p … (⋆s) … (ⓐ#0.#2))
+[ /2 width=1 by/
+| /4 width=1 by cnv_sort, cnv_zero, cnv_lref/
+| @cnv_zero
+  @cnv_bind //
+  @(cnv_appl … 1 p … (⋆s) … (⋆s))
+  [ /2 width=1 by/
+  | /2 width=1 by cnv_sort, cnv_zero/
+  | /4 width=1 by cnv_sort, cnv_zero, cnv_lref, cnv_bind/
+  | /2 width=3 by cpms_ell, lifts_sort/
+  | /4 width=5 by cpms_lref, cpms_ell, lifts_uni, lifts_sort, lifts_bind/
+  ]
+| /4 width=3 by cpms_lref, cpms_ell, lifts_sort/
+| /5 width=7 by cpms_ell, lifts_bind, lifts_flat, lifts_push_lref, lifts_push_zero, lifts_sort/
+]
+qed.