Medium Sudoku Twelve Logic Puzzles (Vol 1) 
 Chapter 51: Two Medium (DiffLev 5-6) Unimprovable Puzzles (numbers 181-182) 
 
-  Step-by-step instructions for solving  Puzzle 181, (67/144)   Diff: 5/9.9961
 -  Step-by-step instructions for solving  Puzzle 182, (72/144)   Diff: 6/99.9971