diff --git a/include/GModelSpectralExpPlaw.hpp b/include/GModelSpectralExpPlaw.hpp
index bcede29..05a5bd2 100644
--- a/include/GModelSpectralExpPlaw.hpp
+++ b/include/GModelSpectralExpPlaw.hpp
@@ -1,7 +1,7 @@
 /***************************************************************************
  *     GModelSpectralExpPlaw.hpp - Exponential cut off power law model     *
  * ----------------------------------------------------------------------- *
- *  copyright (C) 2010-2014 by Juergen Knoedlseder                         *
+ *  copyright (C) 2010-2015 by Juergen Knoedlseder                         *
  * ----------------------------------------------------------------------- *
  *                                                                         *
  *  This program is free software: you can redistribute it and/or modify   *
@@ -124,10 +124,10 @@ protected:
                     m_inv_ecut(1.0/ecut) {}
         double eval(const double& eng);
     protected:
-        const double& m_norm;      //!< Normalization
-        const double& m_index;     //!< Index
-        double        m_inv_pivot; //!< 1 / Pivot energy
-        double        m_inv_ecut;  //!< 1 / Cut off energy
+        double m_norm;      //!< Normalization
+        double m_index;     //!< Index
+        double m_inv_pivot; //!< 1 / Pivot energy
+        double m_inv_ecut;  //!< 1 / Cut off energy
     };
 
     // Energy flux integration kernel
@@ -143,10 +143,10 @@ protected:
                      m_inv_ecut(1.0/ecut) {}
         double eval(const double& eng);
     protected:
-        const double& m_norm;      //!< Normalization
-        const double& m_index;     //!< Index
-        double        m_inv_pivot; //!< 1 / Pivot energy
-        double        m_inv_ecut;  //!< 1 / Cut off energy
+        double m_norm;      //!< Normalization
+        double m_index;     //!< Index
+        double m_inv_pivot; //!< 1 / Pivot energy
+        double m_inv_ecut;  //!< 1 / Cut off energy
     };
 
     // Protected members
diff --git a/include/GModelSpectralGauss.hpp b/include/GModelSpectralGauss.hpp
index a3f1fc8..5e1a780 100644
--- a/include/GModelSpectralGauss.hpp
+++ b/include/GModelSpectralGauss.hpp
@@ -1,7 +1,7 @@
 /***************************************************************************
  *         GModelSpectralGauss.hpp - Spectral Gaussian model class         *
  * ----------------------------------------------------------------------- *
- *  copyright (C) 2014 by Christoph Deil & Ellis Owen                      *
+ *  copyright (C) 2014-2015 by Christoph Deil & Ellis Owen                 *
  * ----------------------------------------------------------------------- *
  *                                                                         *
  *  This program is free software: you can redistribute it and/or modify   *
@@ -116,9 +116,9 @@ protected:
                      m_sigma(sigma) {}
         double eval(const double& eng);
     protected:
-        const double& m_norm;      //!< Normalization
-        const double& m_mean;      //!< Mean
-        const double& m_sigma;     //!< Sigma
+        double m_norm;  //!< Normalization
+        double m_mean;  //!< Mean
+        double m_sigma; //!< Sigma
     };
 
     // Protected members
diff --git a/include/GModelSpectralLogParabola.hpp b/include/GModelSpectralLogParabola.hpp
index 3adc0d8..312dc76 100644
--- a/include/GModelSpectralLogParabola.hpp
+++ b/include/GModelSpectralLogParabola.hpp
@@ -1,7 +1,7 @@
 /***************************************************************************
  *    GModelSpectralLogParabola.hpp - Log parabola spectral model class    *
  * ----------------------------------------------------------------------- *
- *  copyright (C) 2012-2014 by Michael Mayer                               *
+ *  copyright (C) 2012-2015 by Michael Mayer                               *
  * ----------------------------------------------------------------------- *
  *                                                                         *
  *  This program is free software: you can redistribute it and/or modify   *
@@ -135,13 +135,13 @@ protected:
 
     	// Members
     protected:
-    	const double&  m_norm;       //!< Normalization
-    	const double&  m_index;	     //!< Spectral index at pivot
-    	const double&  m_curvature;  //!< Curvature
-    	const GEnergy& m_pivot;	     //!< Pivot energy
+    	double  m_norm;      //!< Normalization
+    	double  m_index;	 //!< Spectral index at pivot
+    	double  m_curvature; //!< Curvature
+    	GEnergy m_pivot;	 //!< Pivot energy
     };
 
-    // Class to determine the integral energyflux, derviation of flux_kern
+    // Class to determine the integral energy flux, derviation of flux_kern
     class eflux_kern : public flux_kern {
     public:
     	// Constructor
diff --git a/include/GModelSpectralSuperExpPlaw.hpp b/include/GModelSpectralSuperExpPlaw.hpp
index 69de9f7..bb13f8b 100644
--- a/include/GModelSpectralSuperExpPlaw.hpp
+++ b/include/GModelSpectralSuperExpPlaw.hpp
@@ -1,7 +1,7 @@
 /***************************************************************************
  *   GModelSpectralSuperExpPlaw.hpp - Super exp. cut off power law model   *
  * ----------------------------------------------------------------------- *
- *  copyright (C) 2014 by Michael Mayer                                    *
+ *  copyright (C) 2014-2015 by Michael Mayer                               *
  * ----------------------------------------------------------------------- *
  *                                                                         *
  *  This program is free software: you can redistribute it and/or modify   *
@@ -131,11 +131,11 @@ protected:
                     m_index2(index2) {}
         double eval(const double& eng);
     protected:
-        const double& m_norm;      //!< Normalization
-        const double& m_index1;    //!< Index1
-        double        m_inv_pivot; //!< 1 / Pivot energy
-        double        m_inv_ecut;  //!< 1 / Cut off energy
-        const double& m_index2;    //!< Index2
+        double m_norm;      //!< Normalization
+        double m_index1;    //!< Index1
+        double m_inv_pivot; //!< 1 / Pivot energy
+        double m_inv_ecut;  //!< 1 / Cut off energy
+        double m_index2;    //!< Index2
     };
 
     // Energy flux integration kernel
@@ -153,11 +153,11 @@ protected:
                      m_index2(index2) {}
         double eval(const double& eng);
     protected:
-        const double& m_norm;      //!< Normalization
-        const double& m_index1;    //!< Index1
-        double        m_inv_pivot; //!< 1 / Pivot energy
-        double        m_inv_ecut;  //!< 1 / Cut off energy
-        const double& m_index2;    //!< Index2
+        double m_norm;      //!< Normalization
+        double m_index1;    //!< Index1
+        double m_inv_pivot; //!< 1 / Pivot energy
+        double m_inv_ecut;  //!< 1 / Cut off energy
+        double m_index2;    //!< Index2
     };
 
     // Protected members
diff --git a/include/GResponse.hpp b/include/GResponse.hpp
index c9f841e..c03f4bc 100644
--- a/include/GResponse.hpp
+++ b/include/GResponse.hpp
@@ -31,6 +31,7 @@
 #include <string>
 #include "GBase.hpp"
 #include "GFunction.hpp"
+#include "GTime.hpp"
 
 /* __ Forward declarations _______________________________________________ */
 class GEvent;
@@ -38,7 +39,6 @@ class GPhoton;
 class GSource;
 class GEnergy;
 class GEbounds;
-class GTime;
 class GObservation;
 class GModelSky;