diff --git a/src/scrollbar.cpp b/src/scrollbar.cpp
--- a/src/scrollbar.cpp
+++ b/src/scrollbar.cpp
@@ -1,3 +1,12 @@
+/*
+  Copyright © 2014 Uwe Rathmann
+
+  This file is copied from Qwt project; you can redistribute it and/or modify it
+  under the terms of the Qwt License, Version 1.0. You can obtain the original
+  source code and the details of the Qwt License from the Qwt website:
+  http://qwt.sourceforge.net/
+*/
+
 #include <qstyle.h>
 #include <qstyleoption.h>
 #include "scrollbar.h"
diff --git a/src/scrollbar.h b/src/scrollbar.h
--- a/src/scrollbar.h
+++ b/src/scrollbar.h
@@ -1,3 +1,12 @@
+/*
+  Copyright © 2014 Uwe Rathmann
+
+  This file is copied from Qwt project; you can redistribute it and/or modify it
+  under the terms of the Qwt License, Version 1.0. You can obtain the original
+  source code and the details of the Qwt License from the Qwt website:
+  http://qwt.sourceforge.net/
+*/
+
 #ifndef _SCROLLBAR_H
 #define _SCROLLBAR_H 1
 
diff --git a/src/scrollzoomer.cpp b/src/scrollzoomer.cpp
--- a/src/scrollzoomer.cpp
+++ b/src/scrollzoomer.cpp
@@ -1,3 +1,12 @@
+/*
+  Copyright © 2014 Uwe Rathmann
+
+  This file is copied from Qwt project; you can redistribute it and/or modify it
+  under the terms of the Qwt License, Version 1.0. You can obtain the original
+  source code and the details of the Qwt License from the Qwt website:
+  http://qwt.sourceforge.net/
+*/
+
 #include <qevent.h>
 #include <qwt_plot_canvas.h>
 #include <qwt_plot_layout.h>
diff --git a/src/scrollzoomer.h b/src/scrollzoomer.h
--- a/src/scrollzoomer.h
+++ b/src/scrollzoomer.h
@@ -1,3 +1,12 @@
+/*
+  Copyright © 2014 Uwe Rathmann
+
+  This file is copied from Qwt project; you can redistribute it and/or modify it
+  under the terms of the Qwt License, Version 1.0. You can obtain the original
+  source code and the details of the Qwt License from the Qwt website:
+  http://qwt.sourceforge.net/
+*/
+
 #ifndef _SCROLLZOOMER_H
 #define _SCROLLZOOMER_H