Group Puzzles (Sudoku Generalized) Difficult Sudoku Logic Puzzles, Volume 1.
  1. Teaching Logic using Group Puzzles
  2. Solving Group Logic Puzzles
  3. Thirty Difficult (DiffLev 9) Sudoku Puzzles (numbers 1-30)
  4. Thirty Difficult (DiffLev 10) Sudoku Puzzles (numbers 31-60)
  5. Thirty Difficult (DiffLev 11) Sudoku Puzzles (numbers 61-90)
  6. Thirty Difficult (DiffLev 12) Sudoku Puzzles (numbers 91-120)
  7. Thirty Difficult (DiffLev 13) Sudoku Puzzles (numbers 121-150)
  8. Thirty Difficult (DiffLev 14) Sudoku Puzzles (numbers 151-180)