Variations on Sudoku-by5 Logic Puzzles (Vol 1) 
 Chapter 9: Three Perplexing Sudoku-by5 Puzzles (numbers 19-21) 
 
-  Step-by-step instructions for solving  Puzzle 19, (275/369)   Diff: 46/97.6798.7676.4998.5599.9996.2124.6469.5794+
 -  Step-by-step instructions for solving  Puzzle 20, (272/369)   Diff: 52/9987.9534.5689.7574.3D35.8894.4673.1111+
 -  Step-by-step instructions for solving  Puzzle 21, (275/369)   Diff: 58/99.9442.AA34.3465.7944.2765.444D.6378.4599+