diff --git a/include/GDerivative.hpp b/include/GDerivative.hpp
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+++ b/include/GDerivative.hpp
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+/***************************************************************************
+ *                  GDerivative.hpp  -  Derivative class                   *
+ * ----------------------------------------------------------------------- *
+ *  copyright (C) 2011 by Jurgen Knodlseder                                *
+ * ----------------------------------------------------------------------- *
+ *                                                                         *
+ *   This program is free software; you can redistribute it and/or modify  *
+ *   it under the terms of the GNU General Public License as published by  *
+ *   the Free Software Foundation; either version 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ ***************************************************************************/
+/**
+ * @file GDerivative.hpp
+ * @brief GDerivative class interface definition.
+ * @author J. Knodlseder
+ */
+
+#ifndef GDERIVATIVE_HPP
+#define GDERIVATIVE_HPP
+
+/* __ Includes ___________________________________________________________ */
+#include "GFunction.hpp"
+
+
+/***********************************************************************//**
+ * @class GDerivative
+ *
+ * @brief Numerical derivatives class interface defintion
+ *
+ * This class allows to compute numerical derivatives using various methods.
+ * The function to be derived is implemented by the abstract GFunction
+ * class.
+ ***************************************************************************/
+class GDerivative {
+
+public:
+
+    // Constructors and destructors
+    GDerivative(void);
+    explicit GDerivative(GFunction* func);
+    GDerivative(const GDerivative& dx);
+    virtual ~GDerivative(void);
+
+    // Operators
+    GDerivative& operator= (const GDerivative& dx);
+
+    // Methods
+    void             function(GFunction* func) { m_func = func; }
+    const GFunction* function(void) const { return m_func; }
+    double           value(const double& x);
+    double           ridder(const double& x, const double& h, double& err);
+
+protected:
+    // Protected methods
+    void   init_members(void);
+    void   copy_members(const GDerivative& dx);
+    void   free_members(void);
+
+    // Protected data area
+    GFunction* m_func;    //!< Pointer to function
+};
+
+#endif /* GDERIVATIVE_HPP */