Champion level - 250 distinct golden Sudoku - Very hard - Vol. 17: 50 Killer Anti-Knight - 50 - 4 Towers "X" Diagonal - 50 Skyscraper - Anti-Diagonal ... - "X" Diagonal. This is great sudoku for you.
100 HARD Sudoku Puzzle Book for Kids: 120 Pages, Ages 8 -12 | 100 Sudoku Puzzles for Kids, 9x9, With Solutions, Hard Sudoku Puzzle Book, Improve Your Game with Increasing Difficulty and Solutions