--- /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/req_fsle.ma".
+include "static_2/static/reqx.ma".
+
+(* SORT-IRRELEVANT EQUIVALENCE FOR LOCAL ENVIRONMENTS ON REFERRED ENTRIES ***)
+
+(* Properties with syntactic equivalence on referred entries ****************)
+
+lemma req_reqx: ∀L1,L2. ∀T:term. L1 ≡[T] L2 → L1 ≛[T] L2.
+/2 width=3 by rex_co/ qed.
+
+lemma req_reqx_trans: ∀L1,L. ∀T:term. L1 ≡[T] L →
+ ∀L2. L ≛[T] L2 → L1 ≛[T] L2.
+/2 width=3 by req_rex_trans/ qed-.