--- /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 "static_2/static/feqx.ma".
+include "basic_2/rt_computation/csx_reqx.ma".
+
+(* STRONGLY NORMALIZING TERMS FOR EXTENDED PARALLEL RT-TRANSITION ***********)
+
+(* Properties with sort-irrelevant equivalence for closures *****************)
+
+lemma csx_feqx_conf:
+ ∀G1,L1,T1. ❪G1,L1❫ ⊢ ⬈*𝐒 T1 →
+ ∀G2,L2,T2. ❪G1,L1,T1❫ ≛ ❪G2,L2,T2❫ → ❪G2,L2❫ ⊢ ⬈*𝐒 T2.
+#G1 #L1 #T1 #HT1 #G2 #L2 #T2 * -G2 -L2 -T2
+/3 width=3 by csx_reqx_conf, csx_teqx_trans/
+qed-.