--- /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 *)
+(* *)
+(**************************************************************************)
+
+(* Project started Tue Aug 22, 2006 ***************************************)
+
+
+
+(* PREAMBLE
+*)
+
+include "logic/equality.ma".
+include "datatypes/Bool.ma".
+include "NPlus/monoid.ma".
+include "NLE/props.ma".
+include "NLE/nplus.ma".
+
+axiom f_equal_3: \forall (A,B,C,D:Set).
+ \forall (f:A \to B \to C \to D).
+ \forall (x1,x2:A).
+ \forall (y1,y2:B).
+ \forall (z1,z2:C).
+ x1 = x2 \to y1 = y2 \to z1 = z2 \to
+ f x1 y1 z1 = f x2 y2 z2.