diff --git a/dune/matrix-vector/singlenonzerocolumnmatrix.hh b/dune/matrix-vector/singlenonzerocolumnmatrix.hh
index 6b515d456cec51a4ecab4a394aba88e8df3234ac..11697bdf53eb7b6f33b474cb5eea277175acfbbb 100644
--- a/dune/matrix-vector/singlenonzerocolumnmatrix.hh
+++ b/dune/matrix-vector/singlenonzerocolumnmatrix.hh
@@ -9,6 +9,8 @@
 #include <dune/fufem/arithmetic.hh>
 #include <dune/fufem/indexedsliceiterator.hh>
 
+// TODO fix namespcae (also for the MatrixTraits injection down below)
+
 /**
  * \brief A static matrix that has only a single nonzero column
  *
@@ -112,7 +114,7 @@ protected:
 };
 
 
-
+// TODO these are probably outdated.
 namespace Arithmetic
 {
     template<class K, int ROWS, int COLS>
diff --git a/dune/matrix-vector/singlenonzerorowmatrix.hh b/dune/matrix-vector/singlenonzerorowmatrix.hh
index f88b769a5d4d29a0f43572e38b347d8be32b314d..f23123cdbb71e4f50e1fcd3187d2b8f214bba883 100644
--- a/dune/matrix-vector/singlenonzerorowmatrix.hh
+++ b/dune/matrix-vector/singlenonzerorowmatrix.hh
@@ -8,6 +8,9 @@
 
 #include <dune/fufem/arithmetic.hh>
 #include <dune/fufem/indexedsliceiterator.hh>
+
+// TODO fix namespace (also for the MatrixTraits injection down below)
+
 /**
  * \brief A static matrix that has only a single nonzero row
  *
@@ -117,7 +120,7 @@ protected:
 };
 
 
-
+// TODO these are probably outdated.
 namespace Arithmetic
 {
     template<class K, int ROWS, int COLS>