Further Reading
---------------
-* This is excellent, everyone should read: [Monad Transformers Step by Step](http://www.grabmueller.de/martin/www/pub/Transformers.pdf)
+* This is excellent, everyone should read: [Monad Transformers Step by Step](http://www.cs.virginia.edu/~wh5a/personal/Transformers.pdf)
+<!-- also http://web.archive.org/web/20140711174905/http://www.grabmueller.de/martin/www/pub/Transformers.pdf -->
* Read Part III of [All About Monads](http://web.archive.org/web/20071106232016/haskell.org/all_about_monads/html/introIII.html). This link is to an archived version, the main link to haskell.org seems to be broken. Some but not all of this site has been [absorbed into the Haskell wikibook](http://en.wikibooks.org/wiki/Haskell/Monad_transformers).