diff --git a/examples/Placement.hs b/examples/Placement.hs
new file mode 100644
--- /dev/null
+++ b/examples/Placement.hs
@@ -0,0 +1,49 @@
+{-
+Auf wie viele Weisen kann man Spielsteine auf ein 3 x 10-Spielbrett setzen, 
+sodass keine zwei Steine horizontal, vertikal oder diagonal benachbart sind?
+
+(Quelle: Preisaufgabe bei LSGM-Wochenendseminar 2011 in Bennewitz
+http://www.lsgm.de/tiki-index.php?page=Seminare.2011-09)
+
+BUILD:  ghc --make Placement
+RUN  :  ./Placement 3 10
+-}
+
+import OBDD (OBDD)
+import qualified OBDD
+
+import Control.Monad ( guard, forM_ )
+import System.Environment ( getArgs )
+import qualified Data.Set 
+
+type Position = (Int,Int)
+
+positions :: Int -> Int -> [ Position ]
+positions width height = do 
+    a <- [ 1 .. width  ]
+    b <- [ 1 .. height ]
+    return (a,b)
+
+adjacent :: Position -> Position -> Bool
+adjacent (a,b) (c,d) = 
+    abs (a-c) <= 1 && abs (b-d) <= 1
+  
+main = do
+    args <- getArgs
+    case map read args :: [Int] of
+        [] -> mainf 3 10
+        [ width, height ] -> mainf width height
+
+mainf width height = do
+    let ps = positions width height
+    print $ OBDD.number_of_models ( Data.Set.fromList ps )
+          $ OBDD.and $ do
+           p <- ps
+           q <- ps
+           guard $ p < q 
+           guard $ adjacent p q
+           return $ OBDD.or [ OBDD.unit p False, OBDD.unit q False ]
+
+
+
+
diff --git a/examples/Queens.hs b/examples/Queens.hs
new file mode 100644
--- /dev/null
+++ b/examples/Queens.hs
@@ -0,0 +1,77 @@
+{-
+the N Queens problem. The propositional variables
+correspond to the positions on the board.
+It shows how to construct an OBDD
+and how to check some of its properties.
+It also shows that the implementation is not terribly efficient.
+It computes the number of solutions for board size 8
+(the answer is: 92) in approx. 1.6 seconds on my machine.
+
+BUILD:  ghc -O2 Queens
+RUN  :  ./Queens 8
+-}
+
+import OBDD (OBDD)
+import qualified OBDD
+import qualified OBDD.Data (toDot)
+
+import Control.Monad ( guard )
+import System.Environment ( getArgs )
+import qualified Data.Set 
+
+type Position = (Int,Int)
+
+positions :: Int -> [ Position ]
+positions n = do 
+    a <- [ 1 .. n ]
+    b <- [ 1 .. n ]
+    return (a,b)
+
+threatens :: Position -> Position -> Bool
+threatens (a,b) (c,d) = 
+       a == c     -- same column
+    || b == d     -- same row
+    || a+b == c+d -- same diagonal
+    || a-b == c-d -- same antidiagonal
+
+board :: Int -> OBDD Position
+board n = OBDD.and 
+    [ each_column_is_occupied n
+    , no_threats n
+    ]
+
+each_column_is_occupied n = OBDD.and $ do
+    a <- [ 1 .. n ]
+    return $ OBDD.or $ do
+        b <- [ 1 .. n ]
+        return $ OBDD.unit (a,b) True
+
+no_threats n = OBDD.and $ do
+    p <- positions n
+    return $ OBDD.and $ do
+        q <- positions n
+        guard $ p < q
+        guard $ threatens p q
+        return $ OBDD.or [ OBDD.unit p False, OBDD.unit q False ]
+
+main = do
+    args <- getArgs
+    case map read args :: [Int] of
+        [] -> mainf 8
+        [arg] -> mainf arg
+
+mainf n = do
+    let d :: OBDD Position
+        d = board n
+
+    print $ OBDD.size d
+    print $ OBDD.satisfiable d
+
+    print $ OBDD.number_of_models 
+          ( Data.Set.fromList $ positions n )
+          d
+
+    m <- OBDD.some_model d
+    print m
+
+    -- writeFile "Queens.dot" $ OBDD.Data.toDot d
diff --git a/obdd.cabal b/obdd.cabal
--- a/obdd.cabal
+++ b/obdd.cabal
@@ -1,6 +1,6 @@
 Name:                obdd
-Version:             0.3.2
-Cabal-Version:       >= 1.6
+Version:             0.3.3
+Cabal-Version:       >= 1.8
 Build-type: Simple
 Synopsis:            Ordered Reduced Binary Decision Diagrams
 Description:         Construct, combine and query OBDDs;
@@ -12,16 +12,27 @@
 Maintainer:          Johannes Waldmann
 Homepage:	     https://github.com/jwaldmann/haskell-obdd
 
-library
+Source-Repository head
+    Type: git
+    Location: git://github.com/jwaldmann/haskell-obdd.git
+
+Library
     Build-Depends:       base==4.*, random, mtl, containers>=0.5, array
     Hs-Source-Dirs:	     src
     Exposed-Modules:     OBDD OBDD.Data OBDD.Make OBDD.Operation OBDD.Property
     Other-Modules:	     OBDD.IntIntMap, OBDD.VarIntIntMap
     ghc-options: -funbox-strict-fields
 
+test-suite obdd-placement
+    Hs-Source-Dirs : examples
+    Type: exitcode-stdio-1.0
+    Main-Is: Placement.hs
+    Build-Depends: base, containers, obdd
 
-Source-Repository head
-    Type: git
-    Location: git://github.com/jwaldmann/haskell-obdd.git
+test-suite obdd-queens
+    Hs-Source-Dirs : examples
+    Type: exitcode-stdio-1.0
+    Main-Is: Queens.hs
+    Build-Depends: base, containers, obdd