diff --git a/ChangeLog.md b/ChangeLog.md
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -74,3 +74,7 @@
 
 * Twelfth version. Divided a package into four different packages: uniqueness-periods, uniqueness-periods-general, dobutokO-poetry-general and dobutokO-poetry. 
 Removed mmsyn7s from the dependencies. Changed the dependencies. 
+
+## 0.13.0.0 -- 2020-08-16
+
+* Thirteenth version. Fixed issues with being not compiled. 
diff --git a/DobutokO/Poetry/UniquenessPeriodsG.hs b/DobutokO/Poetry/UniquenessPeriodsG.hs
--- a/DobutokO/Poetry/UniquenessPeriodsG.hs
+++ b/DobutokO/Poetry/UniquenessPeriodsG.hs
@@ -9,17 +9,33 @@
 -- to obtain (to some extent) suitable for poetry or music text. This module 
 -- provides a functionality to define more complex uniquenessPeriods functions.
 
+{-# LANGUAGE CPP #-}
+
 module DobutokO.Poetry.UniquenessPeriodsG where
 
+#ifdef __GLASGOW_HASKELL__
+#if __GLASGOW_HASKELL__>=804
+/* code that applies only to GHC 8.4.* and higher versions */
+import GHC.Base (mconcat)
+#endif
+#endif
+
 import qualified Data.Vector as V
 import Data.List ((\\),nubBy)
 import String.Ukrainian.UniquenessPeriods
 
+#ifdef __GLASGOW_HASKELL__
+#if __GLASGOW_HASKELL__<804
+/* code that applies only to GHC 8.2.* and lower versions */
+mconcat = concat
+#endif
+#endif
+
 -- | More complicated and longer variant of the 'uniquenessPeriods' that takes into account the second order structure of uniqueness with 'uniquenessP2' and 
 -- can be therefore more fruitful (probably, it is a hypothesis itself that is needed to be tested). Is provided here as an example of the more complex 
 -- \"uniqueness function\". Uses both 'uniqueness2' and 'uniqueness2n' inside and is actually their composition with some (hopefully, natural) parameter functions.
 uniquenessPeriods2 :: Int -> String -> [Int]
-uniquenessPeriods2 x = uniqueness2n (show7snc) (length) x . uniqueness2 (show7sn6) (uniquenessP2)
+uniquenessPeriods2 x = uniqueness2n (show7snc) (length) x . uniqueness2 (show7s6) (uniquenessP2)
 
 -- | Parameterized way to prepare the result that can be used with 'uniqueness2n'.
 uniqueness2 :: (String -> [[String]]) -> ([[String]] -> [[String]]) -> String -> ([[String]],[String])
@@ -27,7 +43,7 @@
  | null xs = ([],[])
  | otherwise = 
     let ys = f xs
-        y2s = mconcat . g $ ys in (ys,y2s)
+        y2s = concat . g $ ys in (ys,y2s)
 
 -- | Being given two functions as parameters uses them to create a longer list of 'Int' then application of only one of them. Besides, it can take into 
 -- account the possible 0 and to create a non-negative list of 'Int' that can be used e. g. by 'DobutokO.Norms.splitNorm'.
diff --git a/dobutokO-poetry.cabal b/dobutokO-poetry.cabal
--- a/dobutokO-poetry.cabal
+++ b/dobutokO-poetry.cabal
@@ -2,7 +2,7 @@
 -- documentation, see http://haskell.org/cabal/users-guide/
 
 name:                dobutokO-poetry
-version:             0.12.0.0
+version:             0.13.0.0
 synopsis:            Helps to order the 7 or less Ukrainian words to obtain somewhat suitable for poetry or music text
 description:         Helps to order the 7 or less Ukrainian words (or their concatenations) to obtain somewhat suitable for poetry or music text. Can be also used as a research instrument with generalized functions.
 
@@ -20,7 +20,7 @@
 library
   exposed-modules:     DobutokO.Poetry.UniquenessPeriodsG, Main, DobutokO.Poetry.General, DobutokO.Poetry.General.Debug
   -- other-modules:
-  -- other-extensions:    
+  other-extensions:    CPP
   build-depends:       base >=4.7 && <4.15, vector >=0.11 && <0.14, mmsyn3 >=0.1.5 && <1, mmsyn7s >=0.8 && <1, mmsyn6ukr >=0.8 && <1, uniqueness-periods >=0.1 && <1, dobutokO-poetry-general >=0.1 && <1
   -- hs-source-dirs:
   default-language:    Haskell2010
@@ -28,7 +28,7 @@
 executable dobutokO-poetry
   main-is:             Main.hs
   other-modules:       DobutokO.Poetry.UniquenessPeriodsG, DobutokO.Poetry.General, DobutokO.Poetry.General.Debug
-  -- other-extensions: 
+  other-extensions:    CPP
   build-depends:       base >=4.7 && <4.15, vector >=0.11 && <0.14, mmsyn3 >=0.1.5 && <1, mmsyn7s >=0.8 && <1, mmsyn6ukr >=0.8 && <1, uniqueness-periods >=0.1 && <1, dobutokO-poetry-general >=0.1 && <1
   -- hs-source-dirs:
   default-language:    Haskell2010