Add a note about element convergence

diff --git a/include/deal.II/fe/fe_bernardi_raugel.h b/include/deal.II/fe/fe_bernardi_raugel.h
index 6bc189d60446e74c92784c13012a2ba42d29d504..3353dbadc758cefbe62c3d8571614a80299038cb 100644 (file)
--- a/include/deal.II/fe/fe_bernardi_raugel.h
+++ b/include/deal.II/fe/fe_bernardi_raugel.h
@@ -49,6 +49,10 @@ DEAL_II_NAMESPACE_OPEN
  * This element does not support hanging nodes or multigrid in the current
  * implementation.
  *
+ * Some numerical experiments have shown that this element may converge with
+ * first-order when using the BR1-Q0 pair for the mixed Laplace equation in
+ * step-20.
+ *
  */
 template <int dim>
 class FE_BernardiRaugel