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diff --git a/matita/matita/contribs/lambdadelta/basic_2/rt_computation/rsx_csx.ma b/matita/matita/contribs/lambdadelta/basic_2/rt_computation/rsx_csx.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/csx_lsubr.ma".
+include "basic_2/rt_computation/csx_cpxs.ma".
+include "basic_2/rt_computation/jsx_rsx.ma".
+
+(* STRONGLY NORMALIZING REFERRED LOCAL ENV.S FOR UNBOUND RT-TRANSITION ******)
+
+(* Advanced properties ******************************************************)
+
+(* Note: swapping the eliminations to avoid rsx_cpx_trans: no solution found *)
+(* Basic_2A1: uses: lsx_lref_be_lpxs *)
+lemma rsx_pair_lpxs (h) (G):
+      ∀K1,V. ⦃G,K1⦄ ⊢ ⬈*[h] 𝐒⦃V⦄ →
+      ∀K2. G ⊢ ⬈*[h,V] 𝐒⦃K2⦄ → ⦃G,K1⦄ ⊢ ⬈*[h] K2 →
+      ∀I. G ⊢ ⬈*[h,#0] 𝐒⦃K2.ⓑ{I}V⦄.
+#h #G #K1 #V #H
+@(csx_ind_cpxs … H) -V #V0 #_ #IHV0 #K2 #H
+@(rsx_ind … H) -K2 #K0 #HK0 #IHK0 #HK10 #I
+@rsx_intro #Y #HY #HnY
+elim (lpx_inv_pair_sn … HY) -HY #K2 #V2 #HK02 #HV02 #H destruct
+elim (tdeq_dec V0 V2) #HnV02 destruct [ -IHV0 -HV02 -HK0 | -IHK0 -HnY ]
+[ /5 width=5 by rsx_rdeq_trans, lpxs_step_dx, rdeq_pair/
+| @(IHV0 … HnV02) -IHV0 -HnV02
+  [ /2 width=3 by lpxs_cpx_trans/
+  | /3 width=3 by rsx_lpx_trans, rsx_cpx_trans/
+  | /2 width=3 by lpxs_step_dx/
+  ]
+]
+qed.
+
+(* Basic_2A1: uses: lsx_lref_be *)
+lemma rsx_lref_pair_drops (h) (G):
+      ∀K,V. ⦃G,K⦄ ⊢ ⬈*[h] 𝐒⦃V⦄ → G ⊢ ⬈*[h,V] 𝐒⦃K⦄ →
+      ∀I,i,L. ⬇*[i] L ≘ K.ⓑ{I}V → G ⊢ ⬈*[h,#i] 𝐒⦃L⦄.
+#h #G #K #V #HV #HK #I #i elim i -i
+[ #L #H >(drops_fwd_isid … H) -H /2 width=3 by rsx_pair_lpxs/
+| #i #IH #L #H
+  elim (drops_inv_bind2_isuni_next … H) -H // #J #Y #HY #H destruct
+  @(rsx_lifts … (𝐔❴1❵)) /3 width=6 by drops_refl, drops_drop/ (**) (* full auto fails *)
+]
+qed.
+
+(* Main properties **********************************************************)
+
+(* Basic_2A1: uses: csx_lsx *)
+theorem csx_rsx (h): ∀G,L,T. ⦃G,L⦄ ⊢ ⬈*[h] 𝐒⦃T⦄ → G ⊢ ⬈*[h,T] 𝐒⦃L⦄.
+#h #G #L #T @(fqup_wf_ind_eq (Ⓕ) … G L T) -G -L -T
+#Z #Y #X #IH #G #L * * //
+[ #i #HG #HL #HT #H destruct
+  elim (csx_inv_lref … H) -H [ |*: * ]
+  [ /2 width=1 by rsx_lref_atom/
+  | /2 width=3 by rsx_lref_unit/
+  | /4 width=6 by rsx_lref_pair_drops, fqup_lref/
+  ]
+| #p #I #V #T #HG #HL #HT #H destruct
+  elim (csx_fwd_bind_unit … H Void) -H /3 width=1 by rsx_bind_void/
+| #I #V #T #HG #HL #HT #H destruct
+  elim (csx_fwd_flat … H) -H /3 width=1 by rsx_flat/
+]
+qed.