--- /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/unwind2_prototerm_eq.ma".
+include "delayed_updating/unwind/unwind2_path_append.ma".
+include "delayed_updating/syntax/prototerm_constructors.ma".
+
+(* TAILED UNWIND FOR PROTOTERM **********************************************)
+
+(* Constructions with constructors for prototerm ****************************)
+
+lemma unwind2_term_iref_sn (f) (t) (k:pnat):
+ ▼[f∘𝐮❨k❩]t ⊆ ▼[f](𝛕k.t).
+#f #t #k #p * #q #Hq #H0 destruct
+@(ex2_intro … (𝗱k◗𝗺◗q))
+/2 width=1 by in_comp_iref_hd/
+qed-.
+
+lemma unwind2_term_iref_dx (f) (t) (k:pnat):
+ ▼[f](𝛕k.t) ⊆ ▼[f∘𝐮❨k❩]t.
+#f #t #k #p * #q #Hq #H0 destruct
+elim (in_comp_inv_iref … Hq) -Hq #p #Hp #Ht destruct
+/2 width=1 by in_comp_unwind2_path_term/
+qed-.
+
+lemma unwind2_term_iref (f) (t) (k:pnat):
+ ▼[f∘𝐮❨k❩]t ⇔ ▼[f](𝛕k.t).
+/3 width=2 by conj, unwind2_term_iref_sn, unwind2_term_iref_dx/
+qed.