diff --git a/citation-resolve.cabal b/citation-resolve.cabal
--- a/citation-resolve.cabal
+++ b/citation-resolve.cabal
@@ -2,7 +2,7 @@
 -- documentation, see http://haskell.org/cabal/users-guide/
 
 name:                citation-resolve
-version:             0.4.2
+version:             0.4.2.1
 synopsis:            convert document IDs such as DOI, ISBN, arXiv ID to bibliographic reference.
 description:         
   This modules provides a way to convert document identifiers, such
diff --git a/src/Text/CSL/Input/Identifier/Internal.hs b/src/Text/CSL/Input/Identifier/Internal.hs
--- a/src/Text/CSL/Input/Identifier/Internal.hs
+++ b/src/Text/CSL/Input/Identifier/Internal.hs
@@ -51,8 +51,6 @@
 -- | The lens for accessing the map within the Database.
 
 makeClassy ''Database
---db :: Simple Iso Database (Map.Map String String)
---db = iso unDatabase Database
 
 instance Default Database where def = Database Map.empty
 
@@ -67,7 +65,8 @@
   toJSON = Yaml.toJSON . map (over _2 lines) . Map.toList . _databaseMap
 
 
-
+-- | Excecute the program using the given database file. The file will be
+--   created if it didn't exist.
 
 withDatabaseFile :: (MonadIO m, MonadState s m, HasDatabase s) => FilePath -> m a -> m a
 withDatabaseFile fn prog = do
@@ -141,7 +140,7 @@
        , ("isbn"    , resolveISBN    ) ]
 
 
--- resolvers for specific document IDs.
+-- | resolvers for specific document IDs.
 
 resolveDOI :: MonadIO m => RM m String String
 resolveDOI docIDStr = do