Use :doc:`getting-started/periodic-tasks` instead of explicit URL.

Changelog

@@ -205,16 +205,16 @@ News
 
 * now depends on :mod:`pyparsing`
 
-* Added support for using complex crontab-expressions in periodic tasks.  For
+* Added support for using complex crontab-expressions in periodic tasks. For
   example, you can now use::
-  
-    crontab(minute="*/15")
+
+    >>> crontab(minute="*/15")
 
   or even::
 
-    crontab(minute="*/30", hour="8-17,1-2", day_of_week="thu-fri")
+    >>> crontab(minute="*/30", hour="8-17,1-2", day_of_week="thu-fri")
 
-  See also http://ask.github.com/celery/getting-started/periodic-tasks.html
+  See :doc:`getting-started/periodic-tasks`.
 
 * celeryd: Now waits for available pool processes before applying new
   tasks to the pool.