--- a/doc-src/AxClass/body.tex Mon May 22 16:03:43 2000 +0200
+++ b/doc-src/AxClass/body.tex Mon May 22 16:04:32 2000 +0200
@@ -44,7 +44,8 @@
object-logic that directly uses the meta type system, such as Isabelle/HOL
\cite{isabelle-HOL}. Subsequently, we present various examples that are all
formulated within HOL, except the one of \secref{sec:ex-natclass} which is in
-FOL.
+FOL. See also \url{http://isabelle.in.tum.de/library/HOL/AxClass/} and
+\url{http://isabelle.in.tum.de/library/FOL/ex/NatClass.html}.
\input{generated/Semigroups}