improve documentation

[[Imported from SVN: r11287]]

dune/elasticity/common/elasticityhelpers.hh

@@ -124,7 +124,7 @@ namespace Dune {
                 * (Delta<(p+2)%3,(q-2)%3>::delta+u[(p+2)%3][(q-2)%3]);
         }
          
-        /** \brief Compute linearization of the determinant of a deformation gradient
+        /** \brief Compute linearization of the determinant of a deformation gradient. Multiplication with a test function(scalar) gradient, gives the linearization in the direction of the test function.
          *
          *  \param u The displacement gradient(!) at which the determinant is evaluated
          */
@@ -143,7 +143,7 @@ namespace Dune {
                 linDet[i][i] = (u[(i+1)%3][(i+1)%3]+1)*(u[(i+2)%3][(i+2)%3]+1)-u[(i+1)%3][(i+2)%3]*u[(i+2)%3][(i+1)%3]
         }
         
-        /** \brief Compute linearization of the determinant of a deformation gradient
+        /** \brief Compute linearization of the determinant of a deformation gradient. Multiplication with a test function(scalar) gradient, gives the linearization in the direction of the test function.
          *
          *  \param u The displacement gradient(!) at which the determinant is evaluated
          */