units in documentation

git-svn-id: svn://svn.iws.uni-stuttgart.de/DUMUX/dumux/trunk@4842 2fb0f335-1f38-0410-981e-8018bf24f1b0

dumux/boxmodels/common/boxmodel.hh

@@ -203,7 +203,7 @@ public:
     }
 
     /*!
-     * \brief Returns the volume [m^3] of a given control volume.
+     * \brief Returns the volume \f$\mathrm{[m^3]}\f$ of a given control volume.
      *
      * \param globalIdx The global index of the control volume's
      *                  associated vertex