/* Return true iff a clique in L strictly contains c. */
 private boolean findSuperClique(List l, VarSet c) {
   for (Iterator it = l.iterator(); it.hasNext(); ) {
     VarSet c2 = (VarSet) it.next();
     if (c2.containsAll(c)) {
       return true;
     }
   }
   return false;
 }