diff --git a/ChangeLog.md b/ChangeLog.md
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -67,3 +67,7 @@
 
 * Fourth version revised D. Changed the Data.List.InnToOut.Basic module and the documentation for Data.List.InnToOut.Unsafe module.
 
+## 0.4.2.1 -- 2019-11-13
+
+* Fourth version revised E. Changed the documentation for both modules.
+
diff --git a/Data/List/InnToOut/Basic.hs b/Data/List/InnToOut/Basic.hs
--- a/Data/List/InnToOut/Basic.hs
+++ b/Data/List/InnToOut/Basic.hs
@@ -10,17 +10,18 @@
 
 module Data.List.InnToOut.Basic 
   (
-    -- * Operations to apply a function or different functions (some can create an inner list) to an element of the outer list   
+    -- * Operations to apply a function or two different functions to an element of the outer list (some of them create inner list)  
        mapI
        , mapI2
   ) where
 
--- | Function that applies additional function @f :: a -> [a]@ to @a@ if @p a = True@
+-- | Function that applies additional function @f :: a -> [a]@ to @a@ if @p :: a -> Bool@ and @p a = True@
 mapI :: (a -> Bool) -> (a -> [a]) -> [a] -> [a]
 mapI p f = concatMap (\x -> if p x then f x else [x])
 {-#INLINE mapI#-}
 
--- | Function that applies additional function @f :: a -> b@ to @a@ if @p a = True@ and otherwise another function @g :: a -> [b]@  to @[a]@ to obtain @[b]@
+-- | Function that applies additional function @f :: a -> b@ to @a@ if @p :: a -> Bool@ and @p a = True@ and otherwise another 
+-- function @g :: a -> [b]@ to @[a]@ and combines results to obtain @[b]@
 mapI2 :: (a -> Bool) -> (a -> b) -> (a -> [b]) -> [a] -> [b]
 mapI2 p f g = concatMap (\x -> if p x then [f x] else g x)
 {-#INLINE mapI2#-}
diff --git a/Data/List/InnToOut/Unsafe.hs b/Data/List/InnToOut/Unsafe.hs
--- a/Data/List/InnToOut/Unsafe.hs
+++ b/Data/List/InnToOut/Unsafe.hs
@@ -5,12 +5,13 @@
 --
 -- Maintainer  :  olexandr543@yahoo.com
 --
--- Various additional operations on lists that have additional intermediate Monads inside.
+-- Various additional operations on lists that have additional intermediate Monads inside. 
+-- Like the 'unsafePerformIO' function they can have unpredictable behaviour. Use them ONLY if you surely know what you are doing.
 --
 
 module Data.List.InnToOut.Unsafe 
   (
-    -- * Operations to obtain intermediate Monads. Like the 'unsafePerformIO' function they can have unpredictable behaviour. Use them ONLY if you surely know what you are doing.
+    -- * Unsafe (in general) operations that can lead to intermediate Monads. 
        unsafeMapI22M
        ,unsafeMapI2M2
        ,unsafeMapI2M2M   
@@ -18,36 +19,37 @@
        ,unsafeMapI2M1
   ) where
 
--- | Unsafe function in which the second intermediate result @c@ is in the @Monad m@. 
--- It can have unpredictable behaviour. Use it ONLY if you surely know what you are doing. Its your responsibility to check whether 
+-- | Unsafe function in which the second intermediate result @c@ is in the @Monad m@. It appears if the predicate @p :: a -> Bool@ is @False@ on @a@.
+-- It can have unpredictable behaviour. Use it ONLY if you surely know what you are doing. It's your responsibility to check whether 
 -- the code does what you expect.
 unsafeMapI22M :: Monad m => (a -> Bool) -> (a -> b) -> (b -> d) -> (a -> m c) -> (m c -> d) -> [a] -> [d]
 unsafeMapI22M p f1 g f2 h = map (\x -> if p x then g (f1 x) else h (f2 x)) 
 {-#INLINE unsafeMapI22M#-}
 
--- | Unsafe function in which the first intermediate result @b@ is in the @Monad m@. 
--- It can have unpredictable behaviour. Use it ONLY if you surely know what you are doing. Its your responsibility to check whether 
+-- | Unsafe function in which the first intermediate result @b@ is in the @Monad m@. It appears if the predicate @p :: a -> Bool@ is @True@ on @a@.
+-- It can have unpredictable behaviour. Use it ONLY if you surely know what you are doing. It's your responsibility to check whether 
 -- the code does what you expect.
 unsafeMapI2M2 :: Monad m => (a -> Bool) -> (a -> m b) -> (m b -> d) -> (a -> c) -> (c -> d) -> [a] -> [d]
 unsafeMapI2M2 p f1 g f2 h = map (\x -> if p x then g (f1 x) else h (f2 x)) 
 {-#INLINE unsafeMapI2M2#-}
 
--- | Unsafe function in which both the intermediate results @b@ and @c@ are in the Monads. 
--- It can have unpredictable behaviour. Use it ONLY if you surely know what you are doing. Its your responsibility to check whether 
+-- | Unsafe function in which both the intermediate results @b@ and @c@ are in the Monads. They appear whenever the predicate @p :: a -> Bool@ is @True@ or @False@, but 
+-- the first one is used if @p a = True@ and the second one -- if @p a = False@.
+-- It can have unpredictable behaviour. Use it ONLY if you surely know what you are doing. It's your responsibility to check whether 
 -- the code does what you expect.
 unsafeMapI2M2M :: (Monad m0, Monad m) => (a -> Bool) -> (a -> m0 b) -> (m0 b -> d) -> (a -> m c) -> (m c -> d) -> [a] -> [d]
 unsafeMapI2M2M p f1 g f2 h = map (\x -> if p x then g (f1 x) else h (f2 x)) 
 {-#INLINE unsafeMapI2M2M#-}
 
--- | Unsafe function in which the second intermediate result @b@ is in the @Monad m@. 
--- It can have unpredictable behaviour. Use it ONLY if you surely know what you are doing. Its your responsibility to check whether 
+-- | Unsafe function in which the second intermediate result @b@ is in the @Monad m@. It appears if the predicate @p :: a -> Bool@ is @False@ on @a@.
+-- It can have unpredictable behaviour. Use it ONLY if you surely know what you are doing. It's your responsibility to check whether 
 -- the code does what you expect.
 unsafeMapI12M :: Monad m => (a -> Bool) -> (a -> c) -> (a -> m b) -> (m b -> c) -> [a] -> [c]
 unsafeMapI12M p f g h = map (\x -> if p x then f x else h (g x)) 
 {-#INLINE unsafeMapI12M#-}
 
--- | Unsafe function in which the first intermediate result @b@ is in the @Monad m@. 
--- It can have unpredictable behaviour. Use it ONLY if you surely know what you are doing. Its your responsibility to check whether 
+-- | Unsafe function in which the first intermediate result @b@ is in the @Monad m@. It appears if the predicate @p :: a -> Bool@ is @True@ on @a@.
+-- It can have unpredictable behaviour. Use it ONLY if you surely know what you are doing. It's your responsibility to check whether 
 -- the code does what you expect.
 unsafeMapI2M1 :: Monad m => (a -> Bool) -> (a -> m b) -> (m b -> c) -> (a -> c) -> [a] -> [c]
 unsafeMapI2M1 p f g h = map (\x -> if p x then g (f x) else h x) 
diff --git a/mmsyn5.cabal b/mmsyn5.cabal
--- a/mmsyn5.cabal
+++ b/mmsyn5.cabal
@@ -2,7 +2,7 @@
 -- documentation, see http://haskell.org/cabal/users-guide/
 
 name:                mmsyn5
-version:             0.4.2.0
+version:             0.4.2.1
 synopsis:            Various additional operations on lists (some with intermediate Monads)
 description:         A small library to deal with a little bit more complex operations on lists than Data.List module
 homepage:            https://hackage.haskell.org/package/mmsyn5