diff --git a/integrator.cpp b/integrator.cpp
index 2c8a176..20c7463 100644
--- a/integrator.cpp
+++ b/integrator.cpp
@@ -1,9 +1,9 @@
 #include "integrator.h"
 
-//#ifdef GSL_INTEGRATION
+#ifdef GSL_INTEGRATION
 #include "gsl/gsl_integration.h"
 #include "gsl/gsl_errno.h"
-//#endif
+#endif
 
 namespace catima{
     integrator_type integrator;
diff --git a/reactions.h b/reactions.h
index c0eadf9..2318e4d 100644
--- a/reactions.h
+++ b/reactions.h
@@ -17,12 +17,10 @@
 #ifndef REACTIONS_H
 #define REACTIONS_H
 #include "catima/build_config.h"
-#ifdef NUREX
 #include "catima/structures.h"
 #include "catima/config.h"
 #include "catima/integrator.h"
 #include <cmath>
-#endif
 
 namespace catima{
     
@@ -58,17 +56,7 @@ double SigmaR_Kox(int Ap, int Zp, double E, int At, int Zt);
 inline double p_from_T(double T, double M=1.0){
     return M*sqrt(T*T + 2*T*atomic_mass_unit);
 }
-/*
-inline double Ecm_from_T_relativistic(double T, double Ap, double At){
-    double mp = Ap*atomic_mass_unit;
-    double mt = At*atomic_mass_unit;
-    double plab= p_from_T(T,Ap);
-    double elab = sqrt(plab*plab + mp*mp);
-    double ecm = sqrt(mp*mp + mt*mt + 2*elab*mt);
-    double pcm = plab * mt / ecm;
-    return sqrt(pcm*pcm+mp*mp)-mp;
-}
-*/
+
 /// calculates Ecm fom T, return in MeV units
 inline double Ecm_from_T(double T, double Ap, double At){
     return T*Ap*At/(Ap+At);
diff --git a/structures.h b/structures.h
index 53f37ad..154911c 100644
--- a/structures.h
+++ b/structures.h
@@ -87,6 +87,7 @@ namespace catima{
               * Maetrial water({
                   {1,1,2},
                   {16,8,1},
+		  1.0,  // optional density
                 });
               * \endcode
               */