diff --git a/ListTree.cabal b/ListTree.cabal
--- a/ListTree.cabal
+++ b/ListTree.cabal
@@ -1,5 +1,5 @@
 Name:                ListTree
-Version:             0.2.0
+Version:             0.2.1
 Category:            Algorithms
 Synopsis:            Trees and monadic trees expressed as monadic lists where the underlying monad is a list
 Description:
diff --git a/src/Data/List/Tree.hs b/src/Data/List/Tree.hs
--- a/src/Data/List/Tree.hs
+++ b/src/Data/List/Tree.hs
@@ -7,15 +7,12 @@
 -- which can also be seen as a tree, except only its leafs
 -- are accessible and only in "dfs order".
 --
--- > import Control.Monad.Generator
--- > import Control.Monad.Trans
--- > import Data.List.Class (genericTake, takeWhile, toList, lastL)
+-- > import Control.Monad.Trans.List.Funcs (repeatM)
+-- > import Data.List.Class (genericTake, scanl, takeWhile, toList, lastL)
+-- > import Prelude hiding (scanl, takeWhile)
 -- >
--- > bits = generate (t "")
--- > t prev = do
--- >   yield prev
--- >   x <- lift "01"
--- >   t (prev ++ [x])
+-- > appendToEnd xs x = xs ++ [x]
+-- > bits = scanl appendToEnd [] (repeatM "01")
 -- >
 -- > > take 3 (bfsLayers bits)
 -- > [[""],["0","1"],["00","01","10","11"]]
@@ -41,7 +38,7 @@
 -- > ["000","001","010","100","101"]
 --
 module Data.List.Tree (
-  Tree,
+  Tree, TreeT, TreeItemM,
   -- | Search algorithms
   dfs, bfs, bfsLayers,
   bestFirstSearchOn,
@@ -66,15 +63,17 @@
 class (List t, List (ItemM t)) => Tree t
 instance (List t, List (ItemM t)) => Tree t
 
-search :: (List l, MonadPlus (ItemM l)) =>
-  (ItemM l (ItemM l a) -> ItemM l a) -> l a -> ItemM l a
+type TreeT m a = ListT (ListT m) a
+type TreeItemM t = ItemM (ItemM t)
+
+search :: Tree t => (ItemM t (ItemM t a) -> ItemM t a) -> t a -> ItemM t a
 search merge =
   merge . foldrL step mzero
   where
     step a = return . cons a . merge
 
 -- | Iterate a tree in DFS pre-order. (Depth First Search)
-dfs :: (List l, MonadPlus (ItemM l)) => l a -> ItemM l a
+dfs :: Tree t => t a -> ItemM t a
 dfs = search join
 
 -- | Transform a tree into lists of the items in its different layers
@@ -176,7 +175,7 @@
 -- and we prune any subtree whose lower bound is over the known upper bound.
 branchAndBound ::
   (Ord b, Tree t) => (a -> (Maybe b, Maybe b))
-  -> t a -> ListT (ListT (StateT (Maybe b) (ItemM (ItemM t)))) a
+  -> t a -> TreeT (StateT (Maybe b) (TreeItemM t)) a
 branchAndBound boundFunc =
   pruneM cond . transformListMonad (transformListMonad lift)
   where