diff --git a/pymath/expression.py b/pymath/expression.py
index 2e38fbd..5a9c743 100644
--- a/pymath/expression.py
+++ b/pymath/expression.py
@@ -21,7 +21,9 @@ class Expression(object):
             #self._exp = exp
             self.postfix_tokens = str2tokens(exp) # les tokens seront alors stockés dans self.tokens temporairement
         elif type(exp) == list:
-            self.postfix_tokens = exp
+            self.postfix_tokens = flatten_list([tok.postfix_tokens if self.isExpression(tok) else tok for tok in exp])
+
+        self._isExpression = 1
 
     def __str__(self):
         """
@@ -91,9 +93,9 @@ class Expression(object):
                 # Comme on vient de faire le calcul, on peut détruire aussi les deux prochains termes
                 del tokenList[0:3]
 
-            # Et les motifs du gens - A, quand l'operateur est d'arité 1
+            # Et les motifs du gens A -, quand l'operateur est d'arité 1
             elif isNumber(tokenList[0]) \
-                    and isOperator(tokenList[1]) and tokenList[2].arity == 1:
+                    and isOperator(tokenList[1]) and tokenList[1].arity == 1:
                 
                 # S'il y a une opération à faire
                 op1 = tokenList[0]
@@ -119,23 +121,33 @@ class Expression(object):
 
         self.child = Expression(steps[-1])
 
+    def isExpression(self, other):
+        try:
+            other._isExpression
+        except AttributeError:
+                return 0
+        return  1
+
+
 
 def test(exp):
     a = Expression(exp)
     print(a)
-    #for i in a.simplify():
-    #    print(i)
+    for i in a.simplify():
+        print(i)
 
     print("\n")
 
 if __name__ == '__main__':
     Expression.STR_RENDER = txt
-    exp = "2 ^ 3 * 5"
+    exp1 = "2 ^ 3 * 5"
+    test(exp1)
+
+    from pymath.operator import op
+    exp = [2, 3, op.pw, 5, op.mul]
     test(exp)
 
-    from pymath.operator import add, pw, mul
-    exp = [2, 3, pw, 5, mul]
-    test(exp)
+    test([Expression(exp1), Expression(exp), op.add])
 
     exp = "1 + 3 * 5"
     test(exp)
diff --git a/pymath/polynom.py b/pymath/polynom.py
index b016198..eb5d014 100644
--- a/pymath/polynom.py
+++ b/pymath/polynom.py
@@ -146,7 +146,7 @@ class Polynom(object):
 
     def isPolynom(self, other):
         try:
-            exp._isPolynom
+            other._isPolynom
         except AttributeError:
                 return 0
         return  1
@@ -248,7 +248,7 @@ class Polynom(object):
                 if a == 0 or b == 0:
                     elem = 0
                 else:
-                    elem = [a, b, "*"]
+                    elem = Expression([a, b, op.mul])
                 try:
                     if coefs[i+j]==0:
                         coefs[i+j] = elem
@@ -259,20 +259,15 @@ class Polynom(object):
 
         p = Polynom(coefs)
         steps.append(p)
-
+        
         steps += p.simplify()
+        
         return steps
 
     def __rmul__(self, other):
         o_poly = self.conv2poly(other)
 
         return o_poly.__mul__(self)
-    
-    def __div__(self, other):
-        pass
-    
-    def __truediv__(self, other):
-        pass
 
 
 def test(p,q):
@@ -304,20 +299,20 @@ if __name__ == '__main__':
     from .fraction import Fraction
     p = Polynom([1, -2 ])
     q = Polynom([4, 7])
-    #test(p,q)
+    test(p,q)
 
     q = Polynom([0, Fraction(1,2), 0, Fraction(-4,3)])
     #test(p,q)
 
     p = Polynom([1, 1, 1 ])
-    print(p)
+    #print(p)
 
 
     #print("-- Poly étrange --")
-    p = Polynom([1, [2, 3], 4], "x")
-    print(repr(p))
-    for i in p.simplify():
-        print(i)
+    #p = Polynom([1, [2, 3], 4], "x")
+    #print(repr(p))
+    #for i in p.simplify():
+    #    print(i)
     #print("-- Poly étrange --")
     #p = Polynom([1, [[2, 3, "*"], [4,5,"*"]], 4], "x")
     #print(repr(p))