; source 
;   #425, November 7 - November 13: The Weekly Extreme 'Unsolveable' Sudoku Puzzle
;   [Weekly Unsolvable Sudoku](https://www.sudokuwiki.org/weekly_sudoku.asp)
[ 1 _ _ _ 2 _ _ _ _ ]
[ _ 6 9 _ _ 8 5 _ _ ]
[ _ 8 _ _ _ 9 7 1 _ ]
[ _ _ _ 3 _ _ _ _ _ ]
[ 3 5 _ _ _ 6 9 _ _ ]
[ _ _ _ _ _ _ _ 4 _ ]
[ _ _ _ _ _ _ 6 _ _ ]
[ _ 9 _ _ _ _ _ 5 7 ]
[ _ _ 6 _ _ 7 _ 8 9 ]