--- matrix_expression.hpp.orig	2008-05-07 14:30:32.000000000 +0100
+++ matrix_expression.hpp	2008-06-10 17:38:26.736266000 +0100
@@ -10,6 +10,9 @@
 //  GeNeSys mbH & Co. KG in producing this work.
 //
 
+// Modified matrix_reference to construct reference<const E> from reference<E>
+//                                properly, by Kian Ming A. Chai (10 Jun 2008) 
+
 #ifndef _BOOST_UBLAS_MATRIX_EXPRESSION_
 #define _BOOST_UBLAS_MATRIX_EXPRESSION_
 
@@ -49,6 +52,18 @@ namespace boost { namespace numeric { na
         explicit matrix_reference (referred_type &e):
               e_ (e) {}
 
+        // Construction from a reference to a non-const E
+        template <typename nonconstE>
+        BOOST_UBLAS_INLINE
+        explicit matrix_reference (const matrix_reference<nonconstE> &e, 
+				   typename boost::enable_if_c<
+                                         boost::is_const<E>::value &&
+				         boost::is_same<typename boost::remove_const<E>::type,
+				                        nonconstE>::value>::type* = 0):
+	  e_(e.expression()) 
+        {}
+
+
         // Accessors
         BOOST_UBLAS_INLINE
         size_type size1 () const {