diff --git a/lambda.hs b/lambda.hs
index c8a61df..11dceeb 100644
--- a/lambda.hs
+++ b/lambda.hs
@@ -34,15 +34,18 @@ instance (Show s) => Show (Expression s) where
     -- show_ :: Expression String -> String
     where show_ c (EReference n)
             | n >= 0 && n < length c = c !! n
-            | otherwise              = "ERR" -- TODO: Do this better?
-          show_ c (ESymbol s)               = s
-          show_ c (EExpr a b@(EExpr _ _))   = show_ c a ++ " (" ++ show_ c b ++ ")"
-          show_ c (EExpr a b)               = show_ c a ++ " "  ++ show_ c b
-          show_ c (ELambda s e@(EExpr _ _)) = "\\" ++ s ++ ".(" ++ show_ (s : c) e ++ ")"
-          show_ c (ELambda s e)             = "\\" ++ s ++ "."  ++ show_ (s : c) e
+            | otherwise              = "ERR" -- TODO: Deal with errors properly?
+          show_ c (ESymbol s)                             = s
+          show_ c (ELambda s e)                           = "\\" ++ s ++ "."  ++ show_ (s : c) e
+          show_ c (EExpr a@(ELambda _ _) b@(ELambda _ _)) = "(" ++ show_ c a ++ ") (" ++ show_ c b ++ ")"
+          show_ c (EExpr a@(ELambda _ _) b@(EExpr   _ _)) = "(" ++ show_ c a ++ ") (" ++ show_ c b ++ ")"
+          show_ c (EExpr a@(ELambda _ _) b              ) = "(" ++ show_ c a ++ ") "  ++ show_ c b
+          show_ c (EExpr a               b@(ELambda _ _)) =        show_ c a ++  " (" ++ show_ c b ++ ")"
+          show_ c (EExpr a               b@(EExpr   _ _)) =        show_ c a ++  " (" ++ show_ c b ++ ")"
+          show_ c (EExpr a               b)               =        show_ c a ++  " "  ++ show_ c b
 
-instance Eq (Expression s) where
-  (ESymbol _)    == (ESymbol _)    = True
+instance (Eq s) => Eq (Expression s) where
+  (ESymbol a)    == (ESymbol b)    = a == b
   (EReference a) == (EReference b) = a == b
   (EExpr a b)    == (EExpr c d)    = a == c && b == d
   (ELambda _ a)  == (ELambda _ b)  = a == b
@@ -73,7 +76,7 @@ takeWhileUnique l = map fst
                   $ takeWhile (\a -> not $ fst a `elem` snd a)
                   $ zip l (inits l)
 
-evaluate :: Expression s -> [Expression s]
+evaluate :: (Eq s) => Expression s -> [Expression s]
 evaluate = takeWhileUnique . iterate apply
 
 {-
@@ -90,6 +93,9 @@ newtype StrSymbol = StrSymbol String
 instance Show StrSymbol where
   show (StrSymbol s) = s
 
+instance Eq StrSymbol where
+  (StrSymbol a) == (StrSymbol b) = a == b
+
 --instance Read StrSymbol where
 --  read s = StrSymbol s
 
@@ -103,6 +109,7 @@ main = do
   putStrLn "Test nested expressions and parentheses"
   print (_e (_e (_s 1) (_s 2)) (_e (_s 3) (_s 4)))
   print (_e (_e (_s 1) (_e (_s 2) (_s 3))) (_s 4))
+  print (_e (_e (_l 1 (_r 0)) (_e (_l 2 (_r 0)) (_l 3 (_r 0)))) (_l 4 (_r 0)))
   putStrLn "Test references and symbols in lambda expressions"
   print (_l 5 (_l 2 (_e (_s 3) (_r 0))))
   print (_l 5 (_l 2 (_e (_s 3) (_r 1))))