On the other hand, when Option is on the inside, as in LO, failures (which we again represent by `mzero`s from the Option monad, not the List monad's own `mzero`; but here since it's the inner monad we need to `hoist Monad.Option.mzero`) abort the whole computation. (If you instead used the List monad's `mzero`, it'd be ignored by `++` and you'd end with just `Some [30]`.)
-This is fun. Notice the difference it makes whether the second `++` is native to the outer `Monad.List`, or whether it's the inner `Monad.List`'s `++` hoisted into the outer wrapper:
+This is fun. Here is a List around a List. Notice the difference it makes whether the second `++` is native to the outer `Monad.List`, or whether it's the inner `Monad.List`'s `++` hoisted into the outer wrapper:
# module LL = Monad.List.T(Monad.List);;
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 This link is to an archived version, the main link to haskell.org seems to be broken.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).