diff --git a/CHANGELOG.md b/CHANGELOG.md
new file mode 100644
--- /dev/null
+++ b/CHANGELOG.md
@@ -0,0 +1,3 @@
+0.0.1
+
+- Add `NFData` instances
diff --git a/boolean-normal-forms.cabal b/boolean-normal-forms.cabal
--- a/boolean-normal-forms.cabal
+++ b/boolean-normal-forms.cabal
@@ -1,5 +1,5 @@
 name:                boolean-normal-forms
-version:             0.0.0.2
+version:             0.0.1
 synopsis:            Boolean normal form: NNF, DNF & CNF
 description:         The provided types that might be useful in symbolic manipulation of propositional logic expressions.
 license:             MIT
@@ -10,7 +10,7 @@
 category:            Data
 build-type:          Simple
 cabal-version:       >=1.18
-extra-source-files:  README.md
+extra-source-files:  README.md CHANGELOG.md
 extra-doc-files:      doc-formulae/*.svg
 tested-with:
   GHC==7.6.3,
@@ -19,10 +19,6 @@
   GHC==8.0.2,
   GHC==8.2.2
 
-source-repository head
-  type: git
-  location: https://github.com/phadej/boolean-normal-forms.git
-
 library
   hs-source-dirs:      src
   exposed-modules:     Data.Algebra.Boolean.NormalForm,
@@ -45,7 +41,8 @@
                        ScopedTypeVariables
   build-depends:       base        >=4.6   && <4.11,
                        containers  >=0.5   && <0.6,
-                       cond        >=0.4.1 && <0.5
+                       cond        >=0.4.1 && <0.5,
+                       deepseq     >=1.1.0.0 && <1.5
   default-language:    Haskell2010
   ghc-options:         -Wall
 
diff --git a/src/Data/Algebra/Boolean/CNF/List.hs b/src/Data/Algebra/Boolean/CNF/List.hs
--- a/src/Data/Algebra/Boolean/CNF/List.hs
+++ b/src/Data/Algebra/Boolean/CNF/List.hs
@@ -24,6 +24,7 @@
 import Data.Either (partitionEithers)
 import Data.Typeable (Typeable)
 import Data.Foldable (Foldable)
+import Control.DeepSeq (NFData(rnf))
 
 import Data.Algebra.Boolean.NormalForm
 import Data.Algebra.Boolean.Negable hiding (not)
@@ -92,3 +93,6 @@
           p (Left x)               = x
 
   fromFreeBoolean = fromNNF . toBooleanWith toNormalForm
+
+instance NFData a => NFData (CNF a) where
+  rnf (CNF xss) = rnf xss
diff --git a/src/Data/Algebra/Boolean/CNF/Set.hs b/src/Data/Algebra/Boolean/CNF/Set.hs
--- a/src/Data/Algebra/Boolean/CNF/Set.hs
+++ b/src/Data/Algebra/Boolean/CNF/Set.hs
@@ -22,6 +22,7 @@
 import Data.Monoid
 import Data.Typeable (Typeable)
 import Data.Foldable (Foldable)
+import Control.DeepSeq (NFData(rnf))
 
 import Data.Set (Set)
 import qualified Data.Set as Set
@@ -105,3 +106,6 @@
           p (Left x)                              = x
 
   fromFreeBoolean = fromNNF . toBooleanWith toNormalForm
+
+instance NFData a => NFData (CNF a) where
+  rnf (CNF xss) = rnf xss
diff --git a/src/Data/Algebra/Boolean/DNF/List.hs b/src/Data/Algebra/Boolean/DNF/List.hs
--- a/src/Data/Algebra/Boolean/DNF/List.hs
+++ b/src/Data/Algebra/Boolean/DNF/List.hs
@@ -24,6 +24,7 @@
 import Data.Either (partitionEithers)
 import Data.Typeable (Typeable)
 import Data.Foldable (Foldable)
+import Control.DeepSeq (NFData(rnf))
 
 import Data.Algebra.Boolean.NormalForm
 import Data.Algebra.Boolean.Negable hiding (not)
@@ -92,3 +93,6 @@
           q (Left x)               = x
 
   fromFreeBoolean = fromNNF . toBooleanWith toNormalForm
+
+instance NFData a => NFData (DNF a) where
+  rnf (DNF xss) = rnf xss
diff --git a/src/Data/Algebra/Boolean/DNF/Set.hs b/src/Data/Algebra/Boolean/DNF/Set.hs
--- a/src/Data/Algebra/Boolean/DNF/Set.hs
+++ b/src/Data/Algebra/Boolean/DNF/Set.hs
@@ -22,6 +22,7 @@
 import Data.Monoid
 import Data.Typeable (Typeable)
 import Data.Foldable (Foldable)
+import Control.DeepSeq (NFData(rnf))
 
 import Data.Set (Set)
 import qualified Data.Set as Set
@@ -105,3 +106,6 @@
           q (Left x)                              = x
 
   fromFreeBoolean = fromNNF . toBooleanWith toNormalForm
+
+instance NFData a => NFData (DNF a) where
+  rnf (DNF xss) = rnf xss
diff --git a/src/Data/Algebra/Boolean/FreeBoolean.hs b/src/Data/Algebra/Boolean/FreeBoolean.hs
--- a/src/Data/Algebra/Boolean/FreeBoolean.hs
+++ b/src/Data/Algebra/Boolean/FreeBoolean.hs
@@ -17,6 +17,7 @@
 
 import Data.Typeable (Typeable)
 import Data.Foldable (Foldable)
+import Control.DeepSeq (NFData(rnf))
 
 import Data.Algebra.Boolean.CoBoolean
 import Data.Algebra.Boolean.Negable hiding (not)
@@ -56,3 +57,11 @@
   (||)   = FBOr
   (&&)   = FBAnd
   not    = FBNot
+
+instance NFData a => NFData (FreeBoolean a) where
+  rnf (FBValue a) = rnf a
+  rnf (FBNot a)   = rnf a
+  rnf (FBAnd a b) = rnf a `seq` rnf b
+  rnf (FBOr a b)  = rnf a `seq` rnf b
+  rnf FBTrue      = ()
+  rnf FBFalse     = ()
diff --git a/src/Data/Algebra/Boolean/NNF/Set.hs b/src/Data/Algebra/Boolean/NNF/Set.hs
--- a/src/Data/Algebra/Boolean/NNF/Set.hs
+++ b/src/Data/Algebra/Boolean/NNF/Set.hs
@@ -27,6 +27,7 @@
 
 import Data.Typeable (Typeable)
 import Data.Foldable (Foldable)
+import Control.DeepSeq (NFData(rnf))
 
 -- | Boolean formula in Negation Normal Form
 --
@@ -102,3 +103,10 @@
   simplify f (NNFOr xs)    = orList $ map (simplify f) $ Set.toList xs
 
   fromFreeBoolean          = toBooleanWith toNormalForm
+
+instance NFData a => NFData (NNF a) where
+  rnf (NNFValue a) = rnf a
+  rnf (NNFOr a)    = rnf a
+  rnf (NNFAnd a)   = rnf a
+  rnf NNFTrue      = ()
+  rnf NNFFalse     = ()
diff --git a/src/Data/Algebra/Boolean/NNF/Tree.hs b/src/Data/Algebra/Boolean/NNF/Tree.hs
--- a/src/Data/Algebra/Boolean/NNF/Tree.hs
+++ b/src/Data/Algebra/Boolean/NNF/Tree.hs
@@ -26,6 +26,7 @@
 
 import Data.Typeable (Typeable)
 import Data.Foldable (Foldable)
+import Control.DeepSeq (NFData(rnf))
 
 -- | Boolean formula in Negation Normal Form
 --
@@ -93,3 +94,10 @@
   simplify f (NNFOr a b)   = nnfOr (simplify f a) (simplify f b)
 
   fromFreeBoolean          = toBooleanWith toNormalForm
+
+instance NFData a => NFData (NNF a) where
+  rnf (NNFValue a) = rnf a
+  rnf (NNFOr a b)  = rnf a `seq` rnf b
+  rnf (NNFAnd a b) = rnf a `seq` rnf b
+  rnf NNFTrue      = ()
+  rnf NNFFalse     = ()
diff --git a/src/Data/Algebra/Boolean/Negable.hs b/src/Data/Algebra/Boolean/Negable.hs
--- a/src/Data/Algebra/Boolean/Negable.hs
+++ b/src/Data/Algebra/Boolean/Negable.hs
@@ -19,6 +19,7 @@
 
 import Data.Monoid
 import Data.Typeable
+import Control.DeepSeq (NFData(rnf))
 
 import Prelude hiding (not)
 import qualified Prelude as P
@@ -37,6 +38,10 @@
 instance CoBoolean1 Neg where
   toBooleanWith f (Pos x) = f x
   toBooleanWith f (Neg x) = B.not $ f x
+
+instance NFData a => NFData (Neg a) where
+  rnf (Pos a) = rnf a
+  rnf (Neg a) = rnf a
 
 -- | Class to represent invertible values.
 --