diff --git a/.DS_Store b/.DS_Store
Binary files a/.DS_Store and b/.DS_Store differ
diff --git a/Chapter15/Test.hs b/Chapter15/Test.hs
new file mode 100644
--- /dev/null
+++ b/Chapter15/Test.hs
@@ -0,0 +1,34 @@
+-------------------------------------------------------------------------
+--
+--         Test.hs
+--
+-- 	The test module of the Huffman example
+--
+-- 	(c) Addison-Wesley, 1996-2011.
+--
+-------------------------------------------------------------------------
+
+module Test where
+
+-- The test module of the Huffman example
+
+import Main
+import Test.QuickCheck
+import Data.List ( nub )
+
+
+-- QuickCheck testing
+
+checkInverse :: String -> Bool
+
+checkInverse string = 
+    decodeMessage tree (codeMessage table string) == string
+        where
+          tree = codes string
+          table = codeTable tree
+
+-- prop_Hufmann :: String -> Bool
+
+prop_Hufmann string =
+    (length (nub string) > 1) ==> checkInverse string
+    
diff --git a/Chapter16/Store.hs b/Chapter16/Store.hs
new file mode 100644
--- /dev/null
+++ b/Chapter16/Store.hs
@@ -0,0 +1,48 @@
+-------------------------------------------------------------------------
+--  
+-- 	   Store.hs
+--  
+--         An abstract data type of stores of integers, implemented as
+--         a list of pairs of variables and values.			
+-- 									
+--         (c) Addison-Wesley, 1996-2011.					
+--  
+-------------------------------------------------------------------------
+
+module Store 
+   ( Store, 
+     initial,     -- Store
+     value,       -- Store -> Var -> Integer
+     update       -- Store -> Var -> Integer -> Store
+    ) where
+
+-- Var is the type of variables.					
+
+type Var = Char
+
+-- The implementation is given by a newtype declaration, with one
+-- constructor, taking an argument of type [ (Integer,Var) ].
+
+data Store = Store [ (Integer,Var) ] 
+
+instance Eq Store where 
+  (Store sto1) == (Store sto2) = (sto1 == sto2)					
+
+instance Show Store where
+  showsPrec n (Store sto) = showsPrec n sto					
+--  
+initial :: Store 
+
+initial = Store []
+
+value  :: Store -> Var -> Integer
+
+value (Store []) v         = 0
+value (Store ((n,w):sto)) v 
+  | v==w            = n
+  | otherwise       = value (Store sto) v
+
+update  :: Store -> Var -> Integer -> Store
+
+update (Store sto) v n = Store ((n,v):sto)
+
diff --git a/Craft3e.cabal b/Craft3e.cabal
--- a/Craft3e.cabal
+++ b/Craft3e.cabal
@@ -1,6 +1,6 @@
 
 name: Craft3e
-version: 0.1.0.6
+version: 0.1.0.7
 license: MIT
 license-file: LICENSE
 copyright: (c) Addison Wesley