# HG changeset patch
# User Peter Kovacs <kpeter@inf.elte.hu>
# Date 1267406885 -3600
# Node ID 11bd4cea8379ca9de34e3332d9ae7584641c6807
# Parent  edb7d5759e0d57f2600dfc752a8f7a2fe20a0988
Slightly extend LGF section

diff -r edb7d5759e0d -r 11bd4cea8379 lgf.dox
--- a/lgf.dox	Mon Mar 01 02:27:36 2010 +0100
+++ b/lgf.dox	Mon Mar 01 02:28:05 2010 +0100
@@ -109,14 +109,31 @@
     .attribute("caption", title)
     .run();
 \endcode
+
+Undirected graphs can be stored in LGF format in almost the same way.
+The <tt>\@arcs</tt> section can also be called <tt>\@edges</tt>, they are
+identical. The only speciality is that arc maps can be distinguished from
+edge maps using a \c + or \c - prefix before the name of the map.
+For example,
+
+\code
+  @edges
+            label  +length  -length  
+  0    1    0      10       20
+  ...
+\endcode
+
+In conjunction with undirected graphs, the classes \ref GraphReader and
+\ref GraphWriter can be used.
  
-Apart from LGF, the library can also handle other graph
+For more information, see the \ref lgf-format "description of the LGF format"
+and the \ref io_group module in the reference manual.
+For a working example, see \ref lgf_demo.cc in the demo directory
+of the LEMON source.
+
+\note Apart from LGF, the library can also handle other graph
 formats, such as the well-known DIMACS format.
 
-For more information, see a more detailed \ref lgf-format
-"description of the LGF format" and the \ref io_group module
-in the reference manual.
-
 [TRAILER]
 */
 }