Problem solved... sort of: Mathematicians come up with formula to complete every Sudoku (but trying to understand it could take even longer than doing the puzzle) | Daily Mail Online
What is the minimum number of numbers to place on a Sudoku board to solve it? - Quora
Amazon.com: Win At Sudoku - The complete guide to solving all levels of Sudoku puzzles using pure logic (Christmas Gift: FREE Puzzle Book) eBook : Eardley, Caro: Kindle Store
AI Escargot - The Most Difficult Sudoku Puzzle by Arto Inkala (6-Jun-2007) Paperback: Amazon.com: Books
Magic Word Square: Hardest Sudoku Puzzle
World's hardest sudoku: Can you solve Dr Arto Inkala's puzzle? - Mirror Online
It took three months to create, so how long will it take to crack ...the world's hardest Sudoku? | Daily Mail Online
world's hardest sudoku | The Chatterjis Blog
The world's hardest sudoku? | Newspapers | The Guardian
True test of genius or monumental waste of time? Can you solve the hardest ever Sudoku? | Daily Mail Online
Problem solved... sort of: Mathematicians come up with formula to complete every Sudoku (but trying to understand it could take even longer than doing the puzzle) | Daily Mail Online