--- /dev/null
+(**************************************************************************)
+(* ___ *)
+(* ||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/cnr.ma".
+include "basic_2/rt_computation/cprs.ma".
+
+(* CONTEXT-SENSITIVE PARALLEL R-COMPUTATION FOR TERMS ***********************)
+
+(* Inversion lemmas with normal terms for r-transition **********************)
+
+(* Basic_1: was: nf2_pr3_unfold *)
+(* Basic_2A1: was: cprs_inv_cnr1 *)
+lemma cprs_inv_cnr_sn (h) (G) (L):
+ ∀T1,T2. ⦃G,L⦄ ⊢ T1 ➡*[h] T2 → ⦃G,L⦄ ⊢ ➡[h] 𝐍⦃T1⦄ → T1 = T2.
+#h #G #L #T1 #T2 #H @(cprs_ind_sn … H) -T1 //
+#T1 #T0 #HT10 #_ #IH #HT1
+lapply (HT1 … HT10) -HT10 #H destruct /2 width=1 by/
+qed-.