As well as producing our own proofs, we also accept (and encourage!) submissions from players. If you have a proof that you would like to share, then send us an email so we can work something out.
Tough Sudoku, 14/Sept/2005.
Tough Sudoku, 18/Sept/2005 (Bruno).
Tough Sudoku, 18/Sept/2005 (Andrei).
For more sudoku proofs check out
Bruno's Sudoku Proofs