diff --git a/Bezout.hs b/Bezout.hs
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+++ b/Bezout.hs
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+module Bezout(-- *  Extended gcd of integers
+besout ,
+-- * Modular inverse of integer
+inverseMod,shift,pad,trim,trim' ,deg,(+:),mods,mMod,
+-- * Multiplication of polynomials in F_p[x]
+multPolyZ,
+-- * Euclidean division of polynomials for F_p[x]
+		euclideanPolyMod, 
+-- * Extended gcd of polynomials in F_p[x]
+extendedgcdpoly ,
+-- * Inverse of polynomial P modulo polynomial Q in F_p[x]
+		inversePolyMod,
+-- * Pretty form  polynom input
+prettyFormPoly) where
+
+-- besout
+-- | besout compute extended gcd of two integers. For example : "besout" 13 17 = [4,-3,1] , this means that 
+-- gcd of 13 and 17 is 1 and 1 could be written as linear combination of 13 and 17 as 1 = 4*13 - 3*17.
+besout :: Integer -> Integer -> [Integer]
+besout x y = bBesout [1,0,x] [0,1,y]
+	where
+	bBesout u v = case v!!2 of 0 -> u
+		    	           _ -> let q = div (u!!2) (v!!2) in bBesout v [u!!k - q * v!!k | k <- [0..2]]
+-- inverseMod	
+-- | From besout identity we derive the modular inverse of an integer x modulo an integer y . Integers
+-- x and y must be relatively prime , otherwise "inverseMod" returns zero. For example : "inverseMod" 13 17 = 4 , "inverseMod" 17 13 = 10.
+inverseMod :: Integer -> Integer -> Integer
+inverseMod x y = let a = besout x y in
+		case a!!2 of 1 -> mods (a!!0) y
+			     _ -> 0
+
+-- | rightpad
+shift n l = l ++ replicate n 0
+-- | leftpad
+pad n l = replicate n 0 ++ l
+-- | trim
+trim x = dropWhile (== 0) x
+-- | trim'
+trim' x = let y = trim x in if y == [] then [0] else y
+-- deg
+-- | deg 
+deg l = length (trim l) - 1
+-- | (+:) add or abstract two list of different length
+(+:) op p q = let d = (length p) - (length q) in zipWith op (pad (-d) p) (pad d q)
+-- | mods return positve remainder of "mod" operator
+mods :: Integer -> Integer -> Integer
+mods x p = if y >= 0 then y else y + p where y = mod x p 
+
+-- | mMod map "mods" over list of integers
+mMod :: [Integer]-> Integer ->[Integer]
+mMod [] _ = []
+mMod (x:xs) p = (mods x p) : mMod xs p
+
+-- multPolyZ
+-- |multPolyZ compute the product of two polynomial P Q in F_p[x].  
+-- Write ploynom P of degree n as a sequence of coefficients P = [an, a_(n-1),.., a_0].
+--To compute the product of polynomials P,Q we borrow the Horner multiplication rules as described by the following chain.
+--It consists to do n compositions of functions detailed in the following diagramm:
+--Q -> anxQ + a_(n-1)Q
+--	R -> xR + a_(n-2)Q
+--		R -> xR + a_(n-3)Q
+--			R -> xR + a-1Q
+--				...
+--				R -> xR + a_0Q
+--Let f = [2,0,3,2,1::Integer], g = [2,5,-3,1::Integer] in F_7[x].
+--"multPolyZ 7 f g" = [4,3,0,0,3,2,6,1] . 
+-- That means that f*g = 4*x^7 + 3*x^6 + 3*x^3 + 2*x^2 + 6*x + 1  in F_7[x].
+-- Be careful to always use the decreasing order in writing polynoms for multPolyZ .
+multPolyZ :: Integer ->[Integer]->[Integer]-> [Integer]
+multPolyZ _ [0] _ = [0]
+multPolyZ _ _ [0] = [0]
+multPolyZ p f [a] = mMod (map (* a) f) p
+multPolyZ p [a] g = mMod (map (* a) g) p
+multPolyZ p u v = trim' $! hHornP p u v where hHornP p u v = let t = inverseMod (head u) p in let  a = mMod (map (* t) u) p in mMod (map (* (head u)) $ hornP p (tail a) v v) p where hornP p u v z = hrnP p u v z 1 where 
+hrnP p [] v _ _ = v
+hrnP p (u:us) v z s = let w = mMod ( map (* u) z) p in let r = zipWith(+) (v ++ [0]) (pad s w) in hrnP p us r z (s + 1)
+
+-- euclidanPolyMod
+-- | "euclidanPolyMod" compute the quotient and remainder of euclidean division of polynomial P by
+--  Q in the ring F_p[x] where p is a prime number.
+-- Let f = [2,0,3,2,1::Integer], g = [2,5,-3,1::Integer] in F_7[x].
+-- "euclideanPolyMod" 7 f g = [[1,1],[1,4,0]].
+-- That means f = (x + 1 )*g + (x^2 + 4*x ) in F_7[x].
+euclideanPolyMod :: Integer -> [Integer]-> [Integer]-> [[Integer]]
+euclideanPolyMod p f [1] = [mMod f p , [0] ]
+euclideanPolyMod p f g  = let x = zPolyMod p (trim $! mMod f p) (trim $! mMod g p) in
+			case x!!0 of [] -> [[0],x!!1]
+				     _ -> case x!!1 of [] -> [x!!0 , [0]]
+						       _ -> x	
+	where
+	zPolyMod p f g = let y = head g in if y == 1 then polyQuotRemMod p f g else let a = (inverseMod y p) in let g' = mMod ( map (* a) g) p in let qr = polyQuotRemMod p f g' in [mMod ( map (* a) $! (head qr)) p, last qr]
+			where
+				polyQuotRemMod _ f [] = [f,[]]
+				polyQuotRemMod _ [] g = [[],g]
+				polyQuotRemMod p f g = aux p (trim f) (trim g) []
+	 	 			where aux p f s q | ddif < 0 = [q , f]
+					    		  | otherwise = aux p f' s q'
+	     	      					where ddif = (deg f) - (deg s)
+		    	             			      a = mods (head f) p
+		      	             			      gs = mMod (map (* a) $ shift ddif s) p
+		      	             			      q' = mMod (trim $ (+:) (+) q $ shift ddif [a]) p
+		       	             			      f' = mMod (trim $ tail $ (+:) (-) f gs) p
+
+
+-- extendedgcdpoly
+-- | "extendedgcdpoly" compute the extended gcd of polynomials P and Q in the ring F_p[x] where p is a prime number. 
+-- Let f = [2,0,3,2,1::Integer], g = [2,5,-3,1::Integer] in F_7[x]. 
+-- "extendedgcdpoly" 7 f g = [[5,3],[2,6,5],[2,1]] .
+-- This means that the gcd of f and g in F_7[x] is the polynom 2*x+1 , and 2*x + 1 = (5*x + 3)*f + (2*x^2 + 6*x + 5)*g in F_7[x].
+
+extendedgcdpoly :: Integer -> [Integer] -> [Integer] -> [[Integer]]
+extendedgcdpoly p x y = let t = besoutPoly p x y in let z = t!!2 in
+			case length z of 1 -> let r = inverseMod (z!!0) p in [mMod (map (* (r)) $! (t!!k)) p | k <-[0..2]]
+					 _ -> t
+			where 
+			besoutPoly p x y = besoutPoly' p [[1],[0],x] [[0],[1],y]
+				where
+				besoutPoly' p u v = if last v == [0] then u else let q = (head) $! euclideanPolyMod p (last u) (last v) in let z = ( (map (trim')) $! [let x = multPolyZ p q (v!!k) in mMod ((+:) (-) (u!!k) x ) p | k <-[0..2]]) in besoutPoly' p v z
+-- inversePolyMod
+-- | "inversePolyMod" compute the modular inverse of polynomial P(x) modulo Q(x) in F_p[x] . Polynomials 
+-- P and Q must be relatively prime , otherwise it return [0].
+-- Let f = [2,0,3,2,1::Integer], g = [2,5,-3,1::Integer] in F_13[x]. 
+-- "extendedgcdpoly" 13 f g =[[7,3,7],[6,8,4,7],[1]].
+-- So f and g are relatively prime in F_13[x] , and the inverse of f modulo g in F_13[x] is given by 
+-- "inversePolyMod" 13 f g = [7,3,7] . 
+-- Which says that the inverse of ploynomial f denoted f^(-1) is 7*x^2 + 3*x + 7 modulo g in F_13[x]
+inversePolyMod :: Integer -> [Integer] -> [Integer] -> [Integer]
+inversePolyMod p x y = let t = extendedgcdpoly p x y in let z = length $ t!!2 in 
+			case z of 1 -> t!!0
+				  _ -> [0]
+-- prettyFormPoly
+-- | This is a facility for writing non nul terms of polynomial , if f = 5*x^13 + 4*x^5 + (-3)*x^4 + 11*x + 19 , then prettyFormPoly [[5,13],[4,5],[-3,4],[11,1],[19,0]] = [5,0,0,0,0,0,0,0,4,-3,0,0,11,19]
+
+prettyFormPoly :: [[Integer]]->[Integer]
+prettyFormPoly [[]] = []
+prettyFormPoly [[a,b]]=[a]
+prettyFormPoly (x:t:xs) = let z = [x!!0] ++ (replicate (fromIntegral (x!!1 - t!!1 - 1)) 0) in z ++ prettyFormPoly (t:xs)
+
diff --git a/LICENSE b/LICENSE
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--- /dev/null
+++ b/LICENSE
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+Copyright (c) 2013, Abdelwaheb Miled
+
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+    * Redistributions of source code must retain the above copyright
+      notice, this list of conditions and the following disclaimer.
+
+    * Redistributions in binary form must reproduce the above
+      copyright notice, this list of conditions and the following
+      disclaimer in the documentation and/or other materials provided
+      with the distribution.
+
+    * Neither the name of Abdelwaheb Miled nor the names of other
+      contributors may be used to endorse or promote products derived
+      from this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
diff --git a/Setup.hs b/Setup.hs
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--- /dev/null
+++ b/Setup.hs
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+import Distribution.Simple
+main = defaultMain
diff --git a/besout.cabal b/besout.cabal
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--- /dev/null
+++ b/besout.cabal
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+-- Initial besout.cabal generated by cabal init.  For further 
+-- documentation, see http://haskell.org/cabal/users-guide/
+
+-- The name of the package.
+name:                besout
+
+-- The package version.  See the Haskell package versioning policy (PVP) 
+-- for standards guiding when and how versions should be incremented.
+-- http://www.haskell.org/haskellwiki/Package_versioning_policy
+-- PVP summary:      +-+------- breaking API changes
+--                   | | +----- non-breaking API additions
+--                   | | | +--- code changes with no API change
+version:             0.1.0.0
+
+-- A short (one-line) description of the package.
+synopsis:            Extended GCD of polynomials over F_p[x]
+
+-- A longer description of the package.
+-- description:         
+
+-- The license under which the package is released.
+license:             BSD3
+
+-- The file containing the license text.
+license-file:        LICENSE
+
+-- The package author(s).
+author:              Abdelwaheb Miled
+
+-- An email address to which users can send suggestions, bug reports, and 
+-- patches.
+maintainer:          abdelwahebmiled@gmail.com
+
+-- A copyright notice.
+-- copyright:           
+
+category:            Math
+
+build-type:          Simple
+
+-- Constraint on the version of Cabal needed to build this package.
+cabal-version:       >=1.8
+
+
+library
+  -- Modules exported by the library.
+  exposed-modules:     Bezout
+  
+  -- Modules included in this library but not exported.
+  -- other-modules:       
+  
+  -- Other library packages from which modules are imported.
+  build-depends:       base ==4.5.*
+