--- /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 "ground/lib/stream_eq.ma".
+include "ground/lib/stream_tls.ma".
+
+(* ITERATED TAIL FOR STREAMS ************************************************)
+
+(* Properties with stream_eq *)
+
+lemma stream_tls_eq_repl (A) (n):
+ stream_eq_repl A (λt1,t2. ⫰*[n] t1 ≗ ⫰*[n] t2).
+#A #n @(nat_ind_succ … n) -n //
+#n #IH * #n1 #t1 * #n2 #t2 #H
+elim (stream_eq_inv_cons_bi … H) /2 width=7 by/
+qed.