Hard Logic Puzzles & Brain Games for Adults: 500 Puzzles & 12 Puzzle Types (Sudoku, Fillomino, Battleships, Calcudoku, Binary Puzzle, Slitherlink, ... 3 (Challenging Fun Brain Teasers Series)

Logic Puzzles & Brain Games for Adults: 500 Easy to Hard Puzzles & 12 Puzzle Types (Sudoku, Fillomino, Battleships, Calcudoku, Binary Puzzle, ... Numbrix): 4 (Challenging Fun Brain Teasers)

Tricky Logic Puzzles for Adults: 130+ Difficult Puzzles to Challenge Your Brain

Activity Book : Logic Puzzles for Adults & Seniors: 500 Hard Puzzles (Sudoku - Fillomino - Straights - Futoshiki - Binary - Slitherlink - Sudoku X - ... 29 (Brain Games for Adults Series)

Calcudoku Logic Puzzles: 500 Easy to Hard (9x9) :: Keep Your Brain Young: 19 (Brain Games for Adults)