diff -r 1de908281369 -r abc24245d276 doc/groups.dox
--- a/doc/groups.dox	Fri May 15 10:16:48 2015 +0200
+++ b/doc/groups.dox	Sun May 24 17:29:26 2015 +0200
@@ -585,7 +585,7 @@
 In addition, the graph nodes may be \e labeled, i.e. we are given two
 node labelings \f$l_1:V_1\longrightarrow L\f$ and \f$l_2:V_2\longrightarrow
 L\f$ and we require that \f$l_1(u)=l_2(f(u))\f$ holds for all nodes \f$u \in
-G\f$.
+G_1\f$.
 
 */