Futoshiki: 250 Hard Challenging Logic Puzzles 8x8: 23 (Futoshiki Collections)

Futoshiki: 250 Medium to Hard Challenging Logic Puzzles 8x8 (Futoshiki Collections)

Futoshiki X: 250 Medium to Hard Diagonal Challenging Logic Puzzles 8x8: 55 (Futoshiki Collections)

Futoshiki: 250 Medium Challenging Logic Puzzles 6x6: 12 (Futoshiki Collections)

Futoshiki: 250 Easy to Medium Challenging Logic Puzzles 5x5: 9 (Futoshiki Collections)