diff --git a/objective.cabal b/objective.cabal
--- a/objective.cabal
+++ b/objective.cabal
@@ -2,7 +2,7 @@
 -- documentation, see http://haskell.org/cabal/users-guide/
 
 name:                objective
-version:             0.5
+version:             0.5.1
 synopsis:            Extensible objects
 description:         Stateful effect transducer
 homepage:            https://github.com/fumieval/objective
@@ -26,7 +26,7 @@
                      , Data.Functor.PushPull
   -- other-modules:       
   other-extensions:    MultiParamTypeClasses, KindSignatures, TypeFamilies
-  build-depends:       base >=4.5 && <5, transformers >= 0.3 && <0.5, free >= 4.0 && <5, clean-unions < 0.2, profunctors > 4.0 && <5, elevator
+  build-depends:       base >=4.5 && <5, transformers >= 0.3 && <0.5, clean-unions < 0.2, elevator
   ghc-options: -Wall
   hs-source-dirs:      src
   default-language:    Haskell2010
diff --git a/src/Control/Monad/Objective/Class.hs b/src/Control/Monad/Objective/Class.hs
--- a/src/Control/Monad/Objective/Class.hs
+++ b/src/Control/Monad/Objective/Class.hs
@@ -5,7 +5,19 @@
 {-# LANGUAGE FlexibleContexts #-}
 {-# LANGUAGE ConstraintKinds #-}
 {-# LANGUAGE CPP #-}
-
+-----------------------------------------------------------------------------
+-- |
+-- Module      :  Control.Monad.Objective.IO
+-- Copyright   :  (c) Fumiaki Kinoshita 2014
+-- License     :  BSD3
+--
+-- Maintainer  :  Fumiaki Kinoshita <fumiexcel@gmail.com>
+-- Stability   :  experimental
+-- Portability :  non-portable
+--
+-- 'MonadObjective' class and operations
+--
+-----------------------------------------------------------------------------
 module Control.Monad.Objective.Class where
 import Control.Object
 
diff --git a/src/Control/Object.hs b/src/Control/Object.hs
--- a/src/Control/Object.hs
+++ b/src/Control/Object.hs
@@ -1,7 +1,20 @@
-{-# LANGUAGE Rank2Types, MultiParamTypeClasses, FlexibleInstances, FlexibleContexts #-}
-{-# LANGUAGE DeriveFunctor, DeriveDataTypeable #-}
-{-# LANGUAGE FunctionalDependencies, UndecidableInstances #-}
-{-# LANGUAGE TypeOperators, TupleSections, GADTs #-}
+{-# LANGUAGE Rank2Types, FlexibleInstances, FlexibleContexts, TypeOperators, CPP #-}
+#if __GLASGOW_HASKELL__ >= 707
+{-# LANGUAGE DeriveDataTypeable #-}
+#endif
+-----------------------------------------------------------------------------
+-- |
+-- Module      :  Control.Object
+-- Copyright   :  (c) Fumiaki Kinoshita 2014
+-- License     :  BSD3
+--
+-- Maintainer  :  Fumiaki Kinoshita <fumiexcel@gmail.com>
+-- Stability   :  experimental
+-- Portability :  non-portable
+--
+-- Stateful effect transducer: The Mealy machine for effects.
+--
+-----------------------------------------------------------------------------
 module Control.Object (
   -- * Construction
   Object(..),
@@ -14,7 +27,6 @@
   (.>>.),
   transObject,
   adaptObject,
-  sequential,
   -- * Extensible objects
   loner,
   (.|>.),
@@ -26,14 +38,31 @@
 import Control.Monad
 import Data.Typeable
 import Control.Applicative
-import Control.Monad.Free
 import Data.OpenUnion1.Clean
 
 -- | The type 'Object e m' represents objects which can handle messages @e@, perform actions in the environment @m@.
 -- It can be thought of as an automaton that converts effects.
 -- 'Object's can be composed just like functions using '.>>.'; the identity element is 'echo'.
-newtype Object e m = Object { runObject :: forall x. e x -> m (x, Object e m) } deriving Typeable
+newtype Object e m = Object { runObject :: forall x. e x -> m (x, Object e m) }
+#if __GLASGOW_HASKELL__ >= 707
+  deriving (Typeable)
+#else
+instance (Typeable1 f, Typeable1 m) => Typeable (Object f m) where
+  typeOf t = mkTyConApp objectTyCon [typeOf1 (f t), typeOf1 (g t)] where
+    f :: Object f m -> f a
+    f = undefined
+    g :: Object f m -> m a
+    g = undefined
 
+objectTyCon :: TyCon
+#if __GLASGOW_HASKELL__ < 704
+objectTyCon = mkTyCon "Control.Object.Object"
+#else
+objectTyCon = mkTyCon3 "object" "Control.Object" "Object"
+#endif
+{-# NOINLINE objectTyCon #-}
+#endif
+
 -- | Lift a natural transformation into an object.
 liftO :: Functor f => (forall x. e x -> f x) -> Object e f
 liftO f = Object $ fmap (\x -> (x, liftO f)) . f
@@ -68,14 +97,6 @@
   go s = Object $ liftM (\(a, s') -> (a, go s')) . flip runStateT s . h
 {-# INLINE stateful #-}
 
--- | Convert a /method sequence/ into a sequential /method execution/.
-sequential :: Monad m => Object e m -> Object (Free e) m
-sequential obj = Object $ \x -> case x of
-  Pure a -> return (a, sequential obj)
-  Free f -> do
-    (a, obj') <- runObject obj f
-    runObject (sequential obj') a
-
 -- | A mutable variable.
 variable :: Applicative f => s -> Object (State s) f
 variable s = Object $ \m -> let (a, s') = runState m s in pure (a, variable s')
@@ -98,3 +119,4 @@
 p .|>. q = Object $ fmap (fmap (.|>.q)) . runObject p ||> fmap (fmap (p .|>.)) . runObject q
 
 infixr 3 .|>.
+
diff --git a/src/Data/Functor/PushPull.hs b/src/Data/Functor/PushPull.hs
--- a/src/Data/Functor/PushPull.hs
+++ b/src/Data/Functor/PushPull.hs
@@ -1,8 +1,20 @@
 {-# LANGUAGE DeriveFunctor, DeriveDataTypeable, ConstraintKinds, FlexibleContexts #-}
+-----------------------------------------------------------------------------
+-- |
+-- Module      :  Data.Functor.PushPull
+-- Copyright   :  (c) Fumiaki Kinoshita 2014
+-- License     :  BSD3
+--
+-- Maintainer  :  Fumiaki Kinoshita <fumiexcel@gmail.com>
+-- Stability   :  experimental
+-- Portability :  non-portable
+--
+-----------------------------------------------------------------------------
 module Data.Functor.PushPull where
 import Data.Typeable
 import Control.Elevator
 
+-- | The type for asynchronous input/output.
 data PushPull a b r = Push a r | Pull (b -> r) deriving (Functor, Typeable)
 
 instance Tower (PushPull a b)
diff --git a/src/Data/Functor/Request.hs b/src/Data/Functor/Request.hs
--- a/src/Data/Functor/Request.hs
+++ b/src/Data/Functor/Request.hs
@@ -1,9 +1,21 @@
 {-# LANGUAGE DeriveFunctor, DeriveDataTypeable, ConstraintKinds, FlexibleContexts #-}
+-----------------------------------------------------------------------------
+-- |
+-- Module      :  Data.Functor.Request
+-- Copyright   :  (c) Fumiaki Kinoshita 2014
+-- License     :  BSD3
+--
+-- Maintainer  :  Fumiaki Kinoshita <fumiexcel@gmail.com>
+-- Stability   :  experimental
+-- Portability :  non-portable
+--
+-----------------------------------------------------------------------------
 module Data.Functor.Request where
 import Data.Typeable
 import Control.Elevator
 import Control.Monad
 
+-- | 'Request a b' is the type of a request that sends @a@ to receive @b@.
 data Request a b r = Request a (b -> r) deriving (Functor, Typeable)
 
 instance Tower (Request a b)