diff --git a/sc2/src/sc2code/planets/gentopo.c b/sc2/src/sc2code/planets/gentopo.c
index d470c4088..25e77c330 100644
--- a/sc2/src/sc2code/planets/gentopo.c
+++ b/sc2/src/sc2code/planets/gentopo.c
@@ -16,6 +16,8 @@
  *  Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  */
 
+// See doc/devel/planettopo for details.
+
 #include "gfxlib.h"
 #include "mathlib.h"
 #include "planets.h"