Mathematician Claims Breakthrough in Sudoku Puzzle (Scientific American)

Basically, a mathematician used a rarely-used method for proving that 99 Sudoku puzzles with less than 17 clues are unsolvable. (That is, they have multiple possible outcomes. A 'clue' is an initially filled-in number on the Sudoku grid.)

I knew Lummox JR had some interest in Sudoku puzzle generation, so I thought perhaps this would interest him. (And others as well, of course.)
Sudoku puzzle generation and difficulty scoring are very complex issues.
Perhaps this discovery could make that problem a bit easier.
Interestingly enough it looks like the method he used for a proof hinged on an idea I had a while back for discovering difficult puzzles: finding the unavoidable sets and pinning them with a clue. But it should be noted that finding all the unavoidable sets is a difficult endeavor in itself, because there are zillions of them.