I now *DO* vaguely recall when that technique was discussed a while back. And I can see a [perhaps nontrivial?] philosophical/semantic battle over whether it involves "guessing" or not. My take is that it *DOES* involve guessing and so isn't a "legit" Sudoku procedure -- since it begins with "this cell must be x or y... if it is x then <search to some end condition>; else if it is y <search to some end condition>" sure sounds like a "guess" technique; the fact that it ends with "some other cell must be Z" as opposed to "the original cell has to be y" really doesn't change its nature to my view. And so I'm still not convinced that that particular grid can be solved without guessing.. /Bernie\ -- Bernie Cosell Fantasy Farm Fibers mailto:bernie@fantasyfarm.com Pearisburg, VA --> Too many people, too few sheep <--