1.1 --- a/lemon/lgf_writer.h	Mon Jul 28 09:29:30 2008 +0200
     1.2 +++ b/lemon/lgf_writer.h	Tue Jul 29 10:27:36 2008 +0200
     1.3 @@ -934,7 +934,7 @@
     1.4      std::ostream* _os;
     1.5      bool local_os;
     1.6  
     1.7 -    Graph& _graph;
     1.8 +    const Graph& _graph;
     1.9  
    1.10      std::string _nodes_caption;
    1.11      std::string _edges_caption;