diff --git a/Data/PoliMorf.hs b/Data/PoliMorf.hs
deleted file mode 100644
--- a/Data/PoliMorf.hs
+++ /dev/null
@@ -1,94 +0,0 @@
-{-# LANGUAGE OverloadedStrings #-}
-{-# LANGUAGE PatternGuards #-}
-{-# LANGUAGE BangPatterns #-}
-{-# LANGUAGE RecordWildCards #-}
-
--- | The module provides functionality for manipulating PoliMorf, the
--- morphological dictionary for Polish.
-
-module Data.PoliMorf
-( 
--- * Types
-  Form
-, Base
-, POS
-, MSD
-, Tag
-, Cat
-, Entry (..)
-, split
-, pos
-, msd
-, atomic
-
--- * Parsing
-, readPoliMorf
-, parsePoliMorf
-) where
-
-import Control.Applicative ((<$>))
-import Control.Arrow (second)
-import qualified Data.Text as T
-import qualified Data.Text.Lazy as L
-import qualified Data.Text.Lazy.IO as L
-
--- | A form.
-type Form = T.Text
-
--- | A base form.
-type Base = T.Text
-
--- | A part of speech.
-type POS  = T.Text
-
--- | A morphosyntactic description 
-type MSD  = T.Text
-
--- | A morphosyntactic tag. (Tag = POS + MSD)
-type Tag  = T.Text
-
--- | A semantic category.
-type Cat  = T.Text
-
--- | An entry from the PoliMorf dictionary.
-data Entry = Entry
-    { form :: !Form
-    , base :: !Base
-    , tag  :: !Tag
-    , cat  :: !Cat }
-    deriving (Eq, Ord, Show, Read)
-
--- | Split tag.
-split :: Tag -> (POS, MSD)
-split = second (T.drop 1) . T.break (==':')
-
--- | Entry POS.
-pos :: Entry -> POS
-pos = fst . split . tag
-
--- | Entry MSD.
-msd :: Entry -> MSD
-msd = snd . split . tag
-
--- | Is the entry an atomic one?  More precisely, we treat all negative
--- forms starting with ''nie'' and all superlatives starting with ''naj''
--- as non-atomic entries.
-atomic :: Entry -> Bool
-atomic x
-    | "sup" `T.isInfixOf` tag x && "naj" `T.isPrefixOf` form x = False
-    | "neg" `T.isInfixOf` tag x && "nie" `T.isPrefixOf` form x = False
-    | otherwise = True
-
--- | Read the PoliMorf from the file.
-readPoliMorf :: FilePath -> IO [Entry]
-readPoliMorf path = parsePoliMorf <$> L.readFile path
-
--- | Parse the PoliMorf into a list of entries.
-parsePoliMorf :: L.Text -> [Entry]
-parsePoliMorf = map parsePoliRow . L.lines 
-
--- | Get an entry pair from a PoliMorf row.
-parsePoliRow :: L.Text -> Entry
-parsePoliRow row = case map L.toStrict (L.split (=='\t') row) of
-    [_form, _base, _tag, _cat] -> Entry _form _base _tag _cat
-    _   -> error $ "parsePoliRow: invalid row \"" ++ L.unpack row ++ "\""
diff --git a/polimorf.cabal b/polimorf.cabal
--- a/polimorf.cabal
+++ b/polimorf.cabal
@@ -1,5 +1,5 @@
 name:               polimorf
-version:            0.7.0
+version:            0.7.1
 synopsis:           Working with the PoliMorf dictionary
 description:
     The library provides functionality for manipulating PoliMorf, the
@@ -16,6 +16,7 @@
 build-type:         Simple
 
 library
+    hs-source-dirs: src
     build-depends:
         base >= 4 && < 5
       , containers
diff --git a/src/Data/PoliMorf.hs b/src/Data/PoliMorf.hs
new file mode 100644
--- /dev/null
+++ b/src/Data/PoliMorf.hs
@@ -0,0 +1,97 @@
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE PatternGuards #-}
+{-# LANGUAGE BangPatterns #-}
+{-# LANGUAGE RecordWildCards #-}
+
+-- | The module provides functionality for manipulating PoliMorf, the
+-- morphological dictionary for Polish.
+
+module Data.PoliMorf
+( 
+-- * Types
+  Form
+, Base
+, POS
+, MSD
+, Tag
+, Cat
+, Entry (..)
+, split
+, pos
+, msd
+, atomic
+
+-- * Parsing
+, readPoliMorf
+, parsePoliMorf
+) where
+
+import Control.Applicative ((<$>))
+import Control.Arrow (second)
+import qualified Data.Text as T
+import qualified Data.Text.Lazy as L
+import qualified Data.Text.Lazy.IO as L
+
+-- | A word form.
+type Form = T.Text
+
+-- | A base form.
+type Base = T.Text
+
+-- | A part of speech.
+type POS  = T.Text
+
+-- | A morphosyntactic description 
+type MSD  = T.Text
+
+-- | A morphosyntactic tag. (Tag = POS + MSD)
+type Tag  = T.Text
+
+-- | A semantic category.  It will be set to "" when there is
+-- no category assigned to a particular PoliMorf entry.
+type Cat  = T.Text
+
+-- | An entry from the PoliMorf dictionary.
+data Entry = Entry
+    { form :: !Form
+    , base :: !Base
+    , tag  :: !Tag
+    , cat  :: !Cat }
+    deriving (Eq, Ord, Show, Read)
+
+-- | Split tag.
+split :: Tag -> (POS, MSD)
+split = second (T.drop 1) . T.break (==':')
+
+-- | Entry POS.
+pos :: Entry -> POS
+pos = fst . split . tag
+
+-- | Entry MSD.
+msd :: Entry -> MSD
+msd = snd . split . tag
+
+-- | Is the entry an atomic one?  More precisely, we treat all negative
+-- forms starting with ''nie'' and all superlatives starting with ''naj''
+-- as non-atomic entries.
+atomic :: Entry -> Bool
+atomic x
+    | "sup" `T.isInfixOf` tag x && "naj" `T.isPrefixOf` form x = False
+    | "neg" `T.isInfixOf` tag x && "nie" `T.isPrefixOf` form x = False
+    | otherwise = True
+
+-- | Read the PoliMorf from the file.
+readPoliMorf :: FilePath -> IO [Entry]
+readPoliMorf path = parsePoliMorf <$> L.readFile path
+
+-- | Parse the PoliMorf into a list of entries.
+parsePoliMorf :: L.Text -> [Entry]
+parsePoliMorf = map parsePoliRow . L.lines 
+
+-- | Get an entry pair from a PoliMorf row.
+parsePoliRow :: L.Text -> Entry
+parsePoliRow row = case map L.toStrict (L.split (=='\t') row) of
+    _form : _base : _tag : rest -> Entry _form _base _tag $ case rest of
+        []       -> ""
+        (_cat:_) -> _cat
+    _   -> error $ "parsePoliRow: invalid row \"" ++ L.unpack row ++ "\""