+(**************************************************************************)
+(* ___ *)
+(* ||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/syntax/prototerm_proper.ma".
+include "delayed_updating/syntax/prototerm_constructors.ma".
+
+(* PROPER CONDITION FOR PROTOTERM *******************************************)
+
+(* Constructions with prototerm constructors ********************************)
+
+lemma ppc_iref (t) (n):
+ (𝛗n.t) ϵ 𝐏.
+#t #n #p * #q #Hq #H0 destruct //
+qed.