Variations on Difficult Sudoku-by5 Logic Puzzles (Vol 1) 
 Chapter 5: Eight Difficult Education-Xtreme Puzzles (numbers 17-24) 
 
-  Step-by-step instructions for solving  Puzzle 17, (228/369)   Diff: 10/99.9999.8973
 -  Step-by-step instructions for solving  Puzzle 18, (237/369)   Diff: 10/99.9996.9994
 -  Step-by-step instructions for solving  Puzzle 19, (245/369)   Diff: 11/999.9999.9651
 -  Step-by-step instructions for solving  Puzzle 20, (249/369)   Diff: 11/999.9999.9677
 -  Step-by-step instructions for solving  Puzzle 21, (248/369)   Diff: 12/9999.9999.9922
 -  Step-by-step instructions for solving  Puzzle 22, (238/369)   Diff: 14/99.9999.9935.6971
 -  Step-by-step instructions for solving  Puzzle 23, (255/369)   Diff: 14/99.9999.9977.6595
 -  Step-by-step instructions for solving  Puzzle 24, (258/369)   Diff: 14/99.9999.9999.9941