diff --git a/doc/lgf.dox b/doc/lgf.dox
--- a/doc/lgf.dox
+++ b/doc/lgf.dox
@@ -90,6 +90,9 @@
  caption "LEMON test digraph"
 \endcode
 
+The \e LGF can contain extra sections, but there is no restriction on
+the format of such sections.
+
 */
 }