--- /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 "delayed_updating/unwind_k/unwind2_prototerm.ma".
+include "delayed_updating/unwind_k/unwind2_path_append.ma".
+include "ground/lib/subset_overlap.ma".
+
+(* TAILED UNWIND FOR PROTOTERM **********************************************)
+
+(* Destructions with pic ****************************************************)
+
+lemma unwind2_term_des_pic (f) (t):
+ ▼[f]t ≬ 𝐈 → t ≬ 𝐈.
+#f #t * #p * #q #Hq #H0 #Hp destruct
+@(subset_ol_i … Hq) -Hq (**) (* auto does not work *)
+@(unwind2_path_des_pic … Hp)
+qed-.