Difficult Sudoku Twelve Logic Puzzles (Vol 1)
Chapter 30: Two Difficult (DiffLev 12) Headstrongly Puzzles (numbers 139-140)
- Step-by-step instructions for solving Puzzle 139, (90/144) Diff: 12/9956.6499.9943
- Step-by-step instructions for solving Puzzle 140, (90/144) Diff: 12/9898.9965.7871