  8 1|2 7 5|    9
    9|8    |5    
  5 6|9    |8    
#----+-----+-----
6   2|     |4 8  
  7 5|     |  2  
  3 4|     |7   5
#----+-----+-----
    3|    8|     
  6 7|    2|1   8
5   8|6 1  |2    
# problematic puzzle for November 2006 version.
