X-Git-Url: http://matita.cs.unibo.it/gitweb/?a=blobdiff_plain;f=helm%2Fsoftware%2Fmatita%2Flibrary%2Fdidactic%2Fexercises%2Fnatural_deduction1.ma;h=f4508923730b134f904b4f89baa401b4c83fc506;hb=7cb22a7f8107a6cde0b77b7879e04f586a347102;hp=c2778fbc5c0b548296f75fd5e0642810558d411e;hpb=2030cae5f1a588fa6bbea50927030f83a2156d67;p=helm.git

diff --git a/helm/software/matita/library/didactic/exercises/natural_deduction1.ma b/helm/software/matita/library/didactic/exercises/natural_deduction1.ma
index c2778fbc5..f45089237 100644
--- a/helm/software/matita/library/didactic/exercises/natural_deduction1.ma
+++ b/helm/software/matita/library/didactic/exercises/natural_deduction1.ma
@@ -1,3 +1,17 @@
+(**************************************************************************)
+(*       ___	                                                          *)
+(*      ||M||                                                             *)
+(*      ||A||       A project by Andrea Asperti                           *)
+(*      ||T||                                                             *)
+(*      ||I||       Developers:                                           *)
+(*      ||T||       A.Asperti, C.Sacerdoti Coen,                          *)
+(*      ||A||       E.Tassi, S.Zacchiroli                                 *)
+(*      \   /                                                             *)
+(*       \ /        This file is distributed under the terms of the       *)
+(*        v         GNU Lesser General Public License Version 2.1         *)
+(*                                                                        *)
+(**************************************************************************)
+
 (* Istruzioni: 
 
      http://mowgli.cs.unibo.it/~tassi/exercise-natural_deduction.html 
@@ -182,4 +196,4 @@ apply rule (∨_e (G∨¬L) [h6] (⊥) [h6] (⊥));
 	    ]
 	]
 (*END*)
-qed.
\ No newline at end of file
+qed.