diff --git a/README.md b/README.md
--- a/README.md
+++ b/README.md
@@ -123,8 +123,9 @@
 There are two other tools for [Haskell] capable of producing generalized
 counter-examples: [SmartCheck] and [Lazy SmallCheck 2012].
 
-Extrapolate was accepted for presentation at [IFL 2017], a link to a
-pre-symposium proceedings draft paper will be listed here soon.
+Extrapolate was accepted for presentation at [IFL 2017],
+see the pre-symposium proceedings
+[paper about Extrapolate](https://matela.com.br/paper/extrapolate.pdf).
 
 [extrapolate-on-hackage]:          https://hackage.haskell.org/package/extrapolate
 [Extrapolate from Hackage]:        https://hackage.haskell.org/package/extrapolate
diff --git a/extrapolate.cabal b/extrapolate.cabal
--- a/extrapolate.cabal
+++ b/extrapolate.cabal
@@ -1,5 +1,5 @@
 name:                extrapolate
-version:             0.2.2
+version:             0.2.3
 synopsis:            generalize counter-examples of test properties
 description:
   Extrapolate is a tool able to provide generalized counter-examples of test
@@ -31,7 +31,7 @@
 source-repository this
   type:            git
   location:        https://github.com/rudymatela/speculate
-  tag:             v0.2.2
+  tag:             v0.2.3
 
 library
   exposed-modules: Test.Extrapolate
diff --git a/src/Test/Extrapolate/Core.hs b/src/Test/Extrapolate/Core.hs
--- a/src/Test/Extrapolate/Core.hs
+++ b/src/Test/Extrapolate/Core.hs
@@ -23,7 +23,6 @@
   , bgOrd
 
   , Option (..)
-  , options
   , WithOption (..)
   , maxTests
   , extraInstances
@@ -46,7 +45,7 @@
   , matchList
   , newMatches
 
-  , Testable
+  , Testable (..)
   , results
 
   , areInstancesOf
@@ -197,10 +196,7 @@
   name xs  =  name (head xs) ++ "s"
   expr (xs@[])      =  showConstant  ([]    -: xs)
   expr (xs@(y:ys))  =  constant ":"  ((:) ->>: xs) :$ expr y :$ expr ys
-  background xs  =  [ constant "length" (length -:> xs)
-                    , constant "any"    (any    ->:> xs)
-                    , constant "all"    (all    ->:> xs)
-                    , constant "filter" (filter ->:> xs) ]
+  background xs  =  [ constant "length" (length -:> xs) ]
                  ++ [ constant "elem" (elemBy (*==*) ->:> xs) | hasEq (head xs) ]
   instances xs  =  this xs $ instances (head xs)
 -- TODO: add (==) and (/=) when list element type has (==) and (/=)
@@ -351,6 +347,7 @@
   is = tinstances p
 
 generalizationsCEC :: Testable a => Int -> a -> [Expr] -> [(Expr,[Expr])]
+generalizationsCEC n p es | maxConditionSize p <= 0 = []
 generalizationsCEC n p es =
   [ (wc'', gs'')
   | gs <- generalizations is es
diff --git a/tests/test-extrapolate.hs b/tests/test-extrapolate.hs
--- a/tests/test-extrapolate.hs
+++ b/tests/test-extrapolate.hs
@@ -162,11 +162,7 @@
 listBackgroundOK :: Generalizable a => a -> Bool
 listBackgroundOK x = backgroundListOf x `subset` backgroundOf [x]
   where
-  backgroundListOf x = [ constant "length" $ length  -:> [x]
-                       , constant "any"    $ any    ->:> [x]
-                       , constant "all"    $ all    ->:> [x]
-                       , constant "filter" $ filter ->:> [x]
-                       ]
+  backgroundListOf x = [ constant "length" $ length  -:> [x] ]
                      +++ backgroundOf x
 
 maybeBackgroundOK :: Generalizable a => a -> Bool