Variations on Sudoku-by5 Logic Puzzles (Vol 1) 
 Chapter 20: Three Challenging Education-Xtreme Puzzles (numbers 52-54) 
 
-  Step-by-step instructions for solving  Puzzle 52, (262/369)   Diff: 16/9999.9999.9612.4691
 -  Step-by-step instructions for solving  Puzzle 53, (257/369)   Diff: 17/9.9999.9999.9985.5753
 -  Step-by-step instructions for solving  Puzzle 54, (262/369)   Diff: 19/999.9999.9997.44C6.9982