diff --git a/src/UniqueLogic/ST/TF/Example/Verify.hs b/src/UniqueLogic/ST/TF/Example/Verify.hs
--- a/src/UniqueLogic/ST/TF/Example/Verify.hs
+++ b/src/UniqueLogic/ST/TF/Example/Verify.hs
@@ -43,7 +43,10 @@
 tn1 :: (Term.T -> Term.T) -> (a -> b) -> TrackedNumber a -> TrackedNumber b
 tn1 f g (TrackedNumber xt xn) = TrackedNumber (f xt) (g xn)
 
-tn2 :: (Term.T -> Term.T -> Term.T) -> (a -> b -> c) -> TrackedNumber a -> TrackedNumber b -> TrackedNumber c
+tn2 ::
+   (Term.T -> Term.T -> Term.T) ->
+   (a -> b -> c) ->
+   TrackedNumber a -> TrackedNumber b -> TrackedNumber c
 tn2 f g (TrackedNumber xt xn) (TrackedNumber yt yn) =
    TrackedNumber (f xt yt) (g xn yn)
 
@@ -104,7 +107,8 @@
          VerifyConstraint ->
             Sys.updateAndCheck
                (\old new ->
-                  inconsistency Nothing (toTrackedNumber old) (toTrackedNumber new))
+                  inconsistency Nothing
+                     (toTrackedNumber old) (toTrackedNumber new))
                al av act
 
 
@@ -114,7 +118,8 @@
 
 data
    Exception =
-      Exception (Maybe Term.Name) (TrackedNumber Rational) (TrackedNumber Rational)
+      Exception (Maybe Term.Name)
+         (TrackedNumber Rational) (TrackedNumber Rational)
    deriving (Show)
 
 type Variable s = Sys.Variable Track s (TrackedNumber Rational)
@@ -122,7 +127,8 @@
 globalVariable :: (Ref.C s) => Term.Name -> s (Variable s)
 globalVariable name =
    Sys.globalVariable
-      (\al av -> Sys.updateAndCheck (inconsistency $ Just name) al av . logUpdate name)
+      (\al av ->
+         Sys.updateAndCheck (inconsistency $ Just name) al av . logUpdate name)
 
 
 match :: (Eq a) => TrackedNumber a -> TrackedNumber a -> Bool
@@ -146,7 +152,8 @@
 logUpdate name act = do
    tn@(TrackedNumber _ x) <- mapMaybeT UMT.lift act
    MT.lift $ UMT.wrap $ Track $ MT.lift $
-      writer (TrackedNumber (Term.Var name) x, [Assign name $ fmap toRational tn])
+      writer (TrackedNumber (Term.Var name) x,
+                  [Assign name $ fmap toRational tn])
 
 
 example ::
@@ -164,7 +171,6 @@
                 y = Expr.fromVariable yv
             x*3 =:= y/2
             5 =:= 2+x
---            4 =:= 2+x
          MT.lift $ liftM2 (,)
             (Sys.query xv)
             (Sys.query yv))
diff --git a/src/UniqueLogic/ST/TF/System.hs b/src/UniqueLogic/ST/TF/System.hs
--- a/src/UniqueLogic/ST/TF/System.hs
+++ b/src/UniqueLogic/ST/TF/System.hs
@@ -70,12 +70,12 @@
 
 
 type Updater w s a =
-        Ref.T s (Updates w s) -> Ref.T s (Maybe a) ->
-        MaybeT (UMT.Wrap w s) a -> Update w s
+      Ref.T s (Updates w s) -> Ref.T s (Maybe a) ->
+      MaybeT (UMT.Wrap w s) a -> Update w s
 
 type SimpleUpdater w s a =
-        Ref.T s (Updates w s) -> Ref.T s (Maybe a) ->
-        MaybeT s a -> Update w s
+      Ref.T s (Updates w s) -> Ref.T s (Maybe a) ->
+      MaybeT s a -> Update w s
 
 newtype T w s a =
    Cons {run :: WriterT [Ref.T s (Updates w s)] s a}
@@ -98,7 +98,7 @@
 globalVariable ::
    (UMT.C w, Value w a, Ref.C s) =>
    SimpleUpdater w s a -> s (Variable w s a)
-globalVariable triggerUpdate = object triggerUpdate Nothing
+globalVariable updater = object updater Nothing
 
 localVariable :: (C w, Value w a, Ref.C s) => T w s (Variable w s a)
 localVariable = lift $ globalVariable simpleUpdate
@@ -238,8 +238,7 @@
    Variable w s a -> Variable w s b ->
    T w s ()
 assignment2 f (Variable _ al av) b =
-   let triggerUpdate =
-          varUpdate b $ liftM f $ readSTRefM av
+   let triggerUpdate = varUpdate b $ liftM f $ readSTRefM av
    in  lift $
        Ref.modify al (addUpdate triggerUpdate)
 
@@ -252,9 +251,7 @@
    Variable w s a -> Variable w s b -> Variable w s c ->
    T w s ()
 assignment3 f (Variable _ al av) (Variable _ bl bv) c =
-   let triggerUpdate =
-          varUpdate c $
-          liftM2 f (readSTRefM av) (readSTRefM bv)
+   let triggerUpdate = varUpdate c $ liftM2 f (readSTRefM av) (readSTRefM bv)
    in  lift $
        Ref.modify al (addUpdate triggerUpdate) >>
        Ref.modify bl (addUpdate triggerUpdate)
diff --git a/unique-logic-tf.cabal b/unique-logic-tf.cabal
--- a/unique-logic-tf.cabal
+++ b/unique-logic-tf.cabal
@@ -1,6 +1,6 @@
 Cabal-Version:    2.2
 Name:             unique-logic-tf
-Version:          0.5.1.1
+Version:          0.5.1.2
 License:          BSD-3-Clause
 License-File:     LICENSE
 Author:           Henning Thielemann
@@ -10,7 +10,7 @@
 Synopsis:         Solve simple simultaneous equations
 Description:
   Solve a number of equations simultaneously.
-  This is not Computer Algebra,
+  This is not Computer Algebra nor SMT solving,
   better think of a kind of type inference algorithm
   or logic programming with only one allowed solution.
   .
@@ -60,13 +60,18 @@
     We demonstrate that in "UniqueLogic.ST.TF.Example.Verify".
   .
   This variant of the package requires type families.
+  This helps us avoid @Duplicate@ constraints on the variable values,
+  for the cases where there are no duplication checks.
+  .
+  The concept seems to be formerly known as
+  <https://en.wikipedia.org/wiki/Dataflow_language>.
 Tested-With:       GHC==7.4.2
 Build-Type:        Simple
 Extra-Doc-Files:
   Changes.md
 
 Source-Repository this
-  Tag:         0.5.1.1
+  Tag:         0.5.1.2
   Type:        darcs
   Location:    https://hub.darcs.net/thielema/unique-logic-tf/
 
@@ -78,7 +83,7 @@
   Build-Depends:
     data-ref >=0.0 && <0.2,
     transformers >=0.4 && <0.7,
-    semigroups >=0.1 && <1.0,
+    semigroups >=0.1 && <1,
     containers >=0.4 && <0.9,
     utility-ht >=0.0.9 && <0.1,
     base >= 4 && <5