namespace/package seperators since 4.8.1.0 should be replaced "-" by ".", e.g.: "GHC-Base" to "GHC.Base" https://hackage.haskell.org/package/base-4.8.0.0/docs/src/GHC-Base.html https://hackage.haskell.org/package/base-4.8.1.0/docs/src/GHC.Base.html http://hayoo.fh-wedel.de/?query=join -> source leads to http://hackage.haskell.org/package/base/docs/src/GHC-Base.html#join