Reference

Take some time out and sharpen your mind with Puzzles on the Go: Sudoku and other number puzzles. This compact book contains sudoku puzzles ranging in difficulty from level 1 for beginners through to a diabolical level 5. There are also includes a variety of other challenging number puzzles: addoku, binary, kakuro and lotus puzzles. It also includes a handy pen so you can enjoy these puzzles anywhere and anytime!