diff --git a/discopop_library/discopop_optimizer/optimization/validation.py b/discopop_library/discopop_optimizer/optimization/validation.py
index 1b07a48e1..a0fb870d8 100644
--- a/discopop_library/discopop_optimizer/optimization/validation.py
+++ b/discopop_library/discopop_optimizer/optimization/validation.py
@@ -1,3 +1,11 @@
+# This file is part of the DiscoPoP software (http://www.discopop.tu-darmstadt.de)
+#
+# Copyright (c) 2020, Technische Universitaet Darmstadt, Germany
+#
+# This software may be modified and distributed under the terms of
+# the 3-Clause BSD License.  See the LICENSE file in the package base
+# directory for details.
+
 from typing import List, cast
 from discopop_explorer.PETGraphX import EdgeType, NodeID, PETGraphX
 from discopop_library.discopop_optimizer.OptimizerArguments import OptimizerArguments