--- /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/static/lsubss_ssta.ma".
+
+(* LOCAL ENVIRONMENT REFINEMENT FOR STATIC TYPE ASSIGNMENT ******************)
+
+(* Main properties **********************************************************)
+
+theorem lsubss_trans: ∀h,g,L1,L. h ⊢ L1 •⊑[g] L → ∀L2. h ⊢ L •⊑[g] L2 →
+ h ⊢ L1 •⊑[g] L2.
+#h #g #L1 #L #H elim H -L1 -L
+[ #X #H >(lsubss_inv_atom1 … H) -H //
+| #I #L1 #L #W #HL1 #IHL1 #X #H
+ elim (lsubss_inv_pair1 … H) -H * #L2
+ [ #HL2 #H destruct /3 width=1/
+ | #V #l #H1WV #H2WV #HL2 #H1 #H2 destruct /3 width=3/
+ ]
+| #L1 #L #V1 #W1 #l #H1VW1 #H2VW1 #HL1 #IHL1 #X #H
+ elim (lsubss_inv_pair1 … H) -H * #L2
+ [ #HL2 #H destruct /3 width=5/
+ | #V #l0 #_ #_ #_ #_ #H destruct
+ ]
+]
+qed.