diff --git a/library/cadbiom/models/clause_constraints/mcl/CLUnfolder.py b/library/cadbiom/models/clause_constraints/mcl/CLUnfolder.py
index 6842ea39711037f5cdd4b574fa7ccc05ab98717d..8e6cc891a02aab4b536757586bba7c8ad196cb45 100644
--- a/library/cadbiom/models/clause_constraints/mcl/CLUnfolder.py
+++ b/library/cadbiom/models/clause_constraints/mcl/CLUnfolder.py
@@ -288,7 +288,8 @@ class CLUnfolder(object):
         # ordered list of DIMACS codes of the frontier variables/places
         self.frontier_values = [self.__var_code_table[frp] for frp in self.dynamic_system.frontiers]
         self.frontier_values.sort()
-        ## TODO: sort utile ici ???? si non passer en frozenset et supprimer les casts partout ailleurs
+        ## TODO: Utiliser une liste triée est-il utile ici ?
+        ## si non passer utiliser un frozenset et supprimer les casts partout
         ## Cf RawSolution.frontier_pos_and_neg_values BACKWARD, encore utilisé avec index
         ## Cf TestCLUnfolder.test_frontier indexable mais peut etre contourné
 
@@ -1401,7 +1402,7 @@ class CLUnfolder(object):
             In practice, it is a list with the values (Dimacs code)
             of all frontier places of the system.
         :type max_sol: <int>
-        :type vvars: <list <int>>
+        :type vvars: <list <int>> or <frozenset <int>> or any iterable
         :return: A tuple of RawSolution objects
             RawSolution objects contain a solution got from SAT solver with all
             variable parameters from the unfolder
@@ -1525,9 +1526,6 @@ class CLUnfolder(object):
             variable parameters from the unfolder
         :rtype: <tuple <RawSolution>>
         """
-        if LOGGER.getEffectiveLevel() == DEBUG:
-            LOGGER.debug("squery_solve :: vvars : %s", vvars)
-
         # Initialization
         self.init_forward_unfolding()
         # Horizon adjustment
diff --git a/library/cadbiom/models/clause_constraints/mcl/MCLSolutions.py b/library/cadbiom/models/clause_constraints/mcl/MCLSolutions.py
index b681a02f83f1fa876864cd2f9ff373ca523ea4d5..527360f50b962d55712637ce2f1fd3a198034328 100644
--- a/library/cadbiom/models/clause_constraints/mcl/MCLSolutions.py
+++ b/library/cadbiom/models/clause_constraints/mcl/MCLSolutions.py
@@ -246,8 +246,9 @@ class RawSolution(object):
             frontiers (fixed size): 3824
             solution (increasing size): 171231, 228314, 285405, 285453, 400091 etc.
 
-        @param sol: a dimacs solution
-        @return: a dimacs code list of the activation state on the frontier for sol
+        :return: A dimacs code set of the activation state on the frontiers for
+            the current solution.
+        :rtype: <frozenset <int>>
         """
         # Old API
         # jmax = len(self.unfolder.frontier_values)
@@ -305,9 +306,9 @@ class RawSolution(object):
                     j += 1
                     if j == jmax:
                         # all frontiers are found
-                        return fsol
+                        return frozenset(fsol)
                     frontier = frontiers[j]
-        return fsol # never reach this point
+        return frozenset(fsol) # never reach this point
 
     # Useless proposition
     # ps: jmax allows to stop the search when the iteration is made on solution