diff --git a/birds-of-paradise.cabal b/birds-of-paradise.cabal
--- a/birds-of-paradise.cabal
+++ b/birds-of-paradise.cabal
@@ -4,7 +4,7 @@
 -- http://haskell.org/cabal/users-guide/
 
 name:                birds-of-paradise
-version:             0.1.1.0
+version:             0.2.0.0
 synopsis:            Birds of Paradise
 description:         Birds of Paradise is yet another SK combinator library.
 homepage:            https://github.com/cutsea110/birds-of-paradise.git
@@ -21,7 +21,7 @@
   exposed-modules:     Data.Function.Combinator.Birds
   -- other-modules:
   -- other-extensions:
-  build-depends:       base ^>=4.12.0.0
+  build-depends:       base >=4.12.0.0 && <4.14
   hs-source-dirs:      src
   default-language:    Haskell2010
   ghc-options:         -Wall
@@ -31,4 +31,4 @@
   type:                exitcode-stdio-1.0
   hs-source-dirs:      test
   main-is:             MyLibTest.hs
-  build-depends:       base ^>=4.12.0.0
+  build-depends:       base >=4.12.0.0 && <4.14
diff --git a/src/Data/Function/Combinator/Birds.hs b/src/Data/Function/Combinator/Birds.hs
--- a/src/Data/Function/Combinator/Birds.hs
+++ b/src/Data/Function/Combinator/Birds.hs
@@ -56,6 +56,7 @@
 import Unsafe.Coerce (unsafeCoerce)
 
 -- | B
+-- Haskell @('.')@
 bluebird :: (b -> c) -> (a -> b) -> a -> c
 bluebird f g x = f (g x)
 
@@ -72,6 +73,7 @@
 becard f g h x = f (g ( h x))
 
 -- | C
+-- Haskell 'flip'
 cardinal :: (a -> b -> c) -> b -> a -> c
 cardinal f x y = f y x
 
@@ -108,6 +110,7 @@
 hummingbird f x y = f x y x
 
 -- | I
+-- Haskell 'id'
 idiot :: a -> a
 idiot x = x
 
@@ -116,6 +119,7 @@
 jay f x y z = f x (f y z)
 
 -- | K
+-- Haskell 'const'
 kestrel :: a -> b -> a
 kestrel x _ = x
 
@@ -160,6 +164,7 @@
 robin x f y = f y x
 
 -- | S
+-- Haskell @('<*>')@ in 'Applicative'
 starling :: (a -> b -> c) -> (a -> b) -> a -> c
 starling f g x = f x (g x)
 
@@ -188,6 +193,7 @@
 whybird x = x (whybird x)
 
 -- | I*
+-- Haskell @('$')@
 idiot' :: ((a -> b) -> a) -> (a -> b) -> a
 idiot' f g = f g
 
@@ -243,7 +249,7 @@
 --   The omega bird looks as mockingbird mockingbird.
 --   But, I've implemented this as itself, because omega isn't going to stop anyway.
 omega :: a
-omega = omega -- ^ mockingbird mockingbird
+omega = omega -- mockingbird mockingbird
 
 -- | KM
 konstantMocker :: c -> (a -> b) -> b