Difficult Sudoku Twelve Logic Puzzles (Vol 1)
Chapter 18: Two Difficult (DiffLev 9-12) Backpointers Puzzles (numbers 115-116)
- Step-by-step instructions for solving Puzzle 115, (83/144) Diff: 9/9.9996.7962
- Step-by-step instructions for solving Puzzle 116, (87/144) Diff: 12/9967.7899.5472