diff --git a/Control/Category/Structures.hs b/Control/Category/Structures.hs
index 331f912..c2330bb 100644
--- a/Control/Category/Structures.hs
+++ b/Control/Category/Structures.hs
@@ -9,6 +9,10 @@ License     :  MIT
 Maintainer  :  Paweł Nowak <pawel834@gmail.com>
 Stability   :  experimental
 
+This module defines some basic structures in a category in a more fine-grained
+way then "Control.Arrow".
+
+Unfortunately names in this module clash with "Control.Arrow".
 -}
 module Control.Category.Structures where
 
@@ -22,6 +26,7 @@ infixl 3 ***
 infixl 2 +++
 infixl 3 /+/
 
+-- | A category with finite products.
 class Category cat => Products cat where
     first :: cat a b -> cat (a, c) (b, c)
     first a = a *** id
@@ -37,6 +42,7 @@ class Category cat => Products cat where
 instance Monad m => Products (Kleisli m) where
     (***) = (BadArrow.***)
 
+-- | A category with finite coproducts.
 class Category cat => Coproducts cat where
     left :: cat a b -> cat (Either a c) (Either b c)
     left a = a +++ id
@@ -52,6 +58,7 @@ class Category cat => Coproducts cat where
 instance Monad m => Coproducts (Kleisli m) where
     (+++) = (BadArrow.+++)
 
+-- | A category @cat@ is a CatPlus when @cat a b@ is a monoid for all a, b.
 class Category cat => CatPlus cat where
     cempty :: cat a b
     (/+/) :: cat a b -> cat a b -> cat a b
@@ -62,6 +69,7 @@ instance MonadPlus m => CatPlus (Kleisli m) where
     cempty = BadArrow.zeroArrow
     (/+/)  = (BadArrow.<+>)
 
+-- | A category transformer.
 class CategoryTrans t where
     clift :: Category cat => cat a b -> t cat a b
 
diff --git a/Control/SIArrow.hs b/Control/SIArrow.hs
index 2a60e70..a4b3a3e 100644
--- a/Control/SIArrow.hs
+++ b/Control/SIArrow.hs
@@ -10,7 +10,24 @@ Maintainer  :  Paweł Nowak <pawel834@gmail.com>
 Stability   :  experimental
 
 -}
-module Control.SIArrow where
+module Control.SIArrow (
+    -- * Arrow.
+    SIArrow(..),
+    (^>>), (>>^), (^<<), (<<^),
+
+    -- * Functor and applicative.
+    (/$/), (/$~),
+    (/*/), (/*), (*/),
+
+    -- * Signaling errors.
+    sifail, (/?/),
+
+    -- * Combinators.
+    sisequence,
+    sisequence_,
+    sireplicate,
+    sireplicate_
+    ) where
 
 import           Control.Arrow (Kleisli(..))
 import           Control.Category
@@ -24,7 +41,7 @@ import           Prelude hiding (id, (.))
 
 infixr 1 ^>>, >>^
 infixr 1 ^<<, <<^
-infixl 4 /$/, /$~, ~$/, ~$~
+infixl 4 /$/, /$~
 infixl 5 /*/, */, /*
 
 -- Categories.
@@ -75,21 +92,6 @@ ai /$/ f = sipure ai . f
        => ASemiIso' a b' -> cat c b -> cat c a
 ai /$~ h = cloneSemiIso ai . morphed /$/ h
 
--- | > ai ~$/ f = morphed . ai /$/ f
-(~$/) :: (SIArrow cat, HFoldable a', HFoldable a,
-          HUnfoldable a', HUnfoldable a, Rep a' ~ Rep a)
-      => ASemiIso' a' b -> cat c b -> cat c a
-ai ~$/ h = morphed . cloneSemiIso ai /$/ h
-
--- | > ai ~$~ f = morphed . ai . morphed /$/ f
-(~$~) :: (SIArrow cat,
-          HFoldable a, HUnfoldable a,
-          HFoldable b, HUnfoldable b,
-          HFoldable b', HUnfoldable b',
-          Rep b' ~ Rep b, Rep b' ~ Rep a)
-      => ASemiIso b' b' b' b' -> cat c b -> cat c a
-ai ~$~ h = morphed . cloneSemiIso ai . morphed /$/ h
-
 (/*/) :: SIArrow cat => cat () b -> cat () c -> cat () (b, c)
 a /*/ b = unit ^>> (a *** b)