Convert external links to internal links. Fixes #2010.
diff --git a/Doc/howto/regex.rst b/Doc/howto/regex.rst
index cfcae31..cf787e8 100644
--- a/Doc/howto/regex.rst
+++ b/Doc/howto/regex.rst
@@ -1,3 +1,5 @@
+.. _regex-howto:
+
 ****************************
   Regular Expression HOWTO  
 ****************************