diff --git a/sammy/src/salmon/DerivativeList.h b/sammy/src/salmon/DerivativeList.h
index 745ad992dcbffa09d367db8e3678f26be94eb91a..804dd0ec48537da185d04d0de91074e0c3f45117 100644
--- a/sammy/src/salmon/DerivativeList.h
+++ b/sammy/src/salmon/DerivativeList.h
@@ -149,12 +149,22 @@ namespace sammy{
      */
     int getIndexForShared(int col) const;
   private:    
-     void updateRealCol(int col);
-     GridDataList gridData;
-     GridData sharedData;
+    /* For look-up acceleration set up the linking between columns and
+     * index to either shared or "normal colum */
+    void updateRealCol(int col);
 
-     std::vector<std::pair<int,int>> sharedIndices;
-     std::vector<int> realCol;
+    /** the list of "normal" columns */
+    GridDataList gridData;
+
+    /** The list of shared  columns */
+    GridData sharedData;
+
+    /** The isotope to link to for shared column */
+    std::vector<std::pair<int,int>> sharedIndices;
+
+    /* For look-up acceleration set up the linking between columns and
+     * index to either shared or "normal colum */
+    std::vector<int> realCol;
   };
 
   /**