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diff --git a/matita/matita/contribs/lambdadelta/basic_2/rt_transition/cnh_tdeq.ma b/matita/matita/contribs/lambdadelta/basic_2/rt_transition/cnh_tdeq.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_transition/cpr_tdeq.ma".
+include "basic_2/rt_transition/cnh_simple.ma".
+include "basic_2/rt_transition/cnh_drops.ma".
+
+(* NORMAL TERMS FOR HEAD T-UNUNBOUND RT-TRANSITION **************************)
+
+(* Properties with context-free sort-irrelevant equivalence for terms *******)
+
+lemma cnh_dec_tdeq (h) (G) (L):
+      ∀T1. ∨∨ ⦃G,L⦄ ⊢ ⥲[h] 𝐍⦃T1⦄
+            | ∃∃n,T2. ⦃G,L⦄ ⊢ T1 ➡[n,h] T2 & (T1 ≛ T2 → ⊥).
+#h #G #L * *
+[ #s /3 width=5 by cnh_sort, or_introl/
+| #i elim (drops_F_uni L i)
+  [ /3 width=7 by cnh_atom_drops, or_introl/
+  | * * [ #I | * #V ] #K #HLK
+    [ /3 width=8 by cnh_unit_drops, or_introl/
+    | elim (lifts_total V 𝐔❴↑i❵) #W #HVW
+      @or_intror @(ex2_2_intro … W) [1,2: /2 width=7 by cpm_delta_drops/ ] #H
+      lapply (tdeq_inv_lref1 … H) -H #H destruct
+      /2 width=5 by lifts_inv_lref2_uni_lt/
+    | elim (lifts_total V 𝐔❴↑i❵) #W #HVW
+      @or_intror @(ex2_2_intro … W) [1,2: /2 width=7 by cpm_ell_drops/ ] #H
+      lapply (tdeq_inv_lref1 … H) -H #H destruct
+      /2 width=5 by lifts_inv_lref2_uni_lt/
+    ]
+  ]
+| #l /3 width=5 by cnh_gref, or_introl/
+| #p * [ cases p ] #V1 #T1
+  [ elim (cpr_subst h G (L.ⓓV1) T1 0 L V1) [| /2 width=1 by drops_refl/ ] #T2 #X2 #HT12 #HXT2
+    elim (tdeq_dec T1 T2) [ -HT12 #HT12 | #HnT12 ]
+    [ elim (tdeq_inv_lifts_dx … HT12 … HXT2) -T2 #X1 #HXT1 #_ -X2
+      @or_intror @(ex2_2_intro … X1) [1,2: /2 width=4 by cpm_zeta/ ] #H
+      /2 width=7 by tdeq_lifts_inv_pair_sn/
+    | @or_intror @(ex2_2_intro … (+ⓓV1.T2)) [1,2: /2 width=2 by cpm_bind/ ] #H
+      elim (tdeq_inv_pair … H) -H /2 width=1 by/
+    ]
+  | /3 width=5 by cnh_abbr_neg, or_introl/
+  | /3 width=5 by cnh_abst, or_introl/
+  ]
+| * #V1 #T1
+  [ elim (simple_dec_ex T1) [ #HT1 | * #p * #W1 #U1 #H destruct ]
+    [ /3 width=5 by cnh_appl_simple, or_introl/
+    | elim (lifts_total V1 𝐔❴1❵) #X1 #HVX1
+      @or_intror @(ex2_2_intro … (ⓓ{p}W1.ⓐX1.U1)) [1,2: /2 width=3 by cpm_theta/ ] #H
+      elim (tdeq_inv_pair … H) -H #H destruct
+    | @or_intror @(ex2_2_intro … (ⓓ{p}ⓝW1.V1.U1)) [1,2: /2 width=2 by cpm_beta/ ] #H
+      elim (tdeq_inv_pair … H) -H #H destruct
+    ]
+  | @or_intror @(ex2_2_intro … T1) [1,2: /2 width=2 by cpm_eps/ ] #H
+    /2 width=4 by tdeq_inv_pair_xy_y/
+  ]
+]
+qed-.