diff --git a/Algebra/Ring/Noetherian.hs b/Algebra/Ring/Noetherian.hs
--- a/Algebra/Ring/Noetherian.hs
+++ b/Algebra/Ring/Noetherian.hs
@@ -5,13 +5,15 @@
 module Algebra.Ring.Noetherian ( NoetherianRing, Ideal(..), addToIdeal, toIdeal, appendIdeal
                                , generators, filterIdeal, mapIdeal, principalIdeal) where
 import           Algebra.Internal
-import           Data.Complex
+import qualified Data.Complex            as C
 import           Data.Function
 import           Data.Ord
 import           Data.Ratio
 import           Numeric.Algebra
-import           Prelude          hiding (negate, subtract, (*), (+), (-))
-import qualified Prelude          as P
+import qualified Numeric.Algebra.Complex as NA
+import           Prelude                 hiding (negate, subtract, (*), (+),
+                                          (-))
+import qualified Prelude                 as P
 
 class (Commutative r, Ring r) => NoetherianRing r where
 
@@ -19,7 +21,8 @@
 
 instance NoetherianRing Integer where
 
-instance (Commutative (Complex r), Ring (Complex r)) => NoetherianRing (Complex r) where
+instance (Commutative (NA.Complex r), Ring (NA.Complex r)) => NoetherianRing (NA.Complex r) where
+instance (Commutative (C.Complex r), Ring (C.Complex r)) => NoetherianRing (C.Complex r) where
 instance Integral n => NoetherianRing (Ratio n)
 
 instance Division (Ratio Integer) where
diff --git a/computational-algebra.cabal b/computational-algebra.cabal
--- a/computational-algebra.cabal
+++ b/computational-algebra.cabal
@@ -2,7 +2,7 @@
 -- further documentation, see http://haskell.org/cabal/users-guide/
 
 name:                computational-algebra
-version:             0.1.0.1
+version:             0.1.1.0
 synopsis:            Well-kinded computational algebra library, currently supporting Groebner basis.
 description:         Dependently-typed computational algebra libray for Groebner basis.
 homepage:            https://github.com/konn/computational-algebra
diff --git a/examples/bench.hs b/examples/bench.hs
--- a/examples/bench.hs
+++ b/examples/bench.hs
@@ -9,8 +9,8 @@
 import qualified Numeric.Algebra                         as NA
 import           Progression.Main
 
-x, y, z, w, s, a, b, c :: Polynomial Rational (S (S (S Three)))
-[x, y, z, w, s, a, b, c] = genVars (sS (sS (sS Three)))
+x, y, z, w, s, a, b, c :: Polynomial Rational
+[x, y, z, w, s, a, b, c] = map (injectVar . flip Variable Nothing) "xyzwSabc"
 
 instance NFData Variable where
   rnf (Variable x y) = rnf x `seq` rnf y `seq` ()
@@ -28,7 +28,7 @@
 main :: IO ()
 main =
     defaultMain $ bgroup "groebner"
-                    [ bench "simple" $ nf (simpleBuchberger Lex) ideal3
-                    , bench "relprime" $ nf (primeTestBuchberger Lex) ideal3
-                    , bench "relprime" $ nf (syzygyBuchberger Lex) ideal3
+                    [ bench "simple" $ nf (simpleBuchbergerWith Lex) ideal3
+                    , bench "relprime" $ nf (primeTestBuchbergerWith Lex) ideal3
+                    , bench "syzygy" $ nf (syzygyBuchbergerWith Lex) ideal3
                     ]