Variations on Advanced Sudoku Logic Puzzles (Vol 1) 
 Chapter 45: Four Easy Sudoku-16 Puzzles (numbers 149-152) 
 
-  Step-by-step instructions for solving  Puzzle 149, (86/256)   Diff: 3/993
 -  Step-by-step instructions for solving  Puzzle 150, (86/256)   Diff: 3/992
 -  Step-by-step instructions for solving  Puzzle 151, (95/256)   Diff: 3/997
 -  Step-by-step instructions for solving  Puzzle 152, (108/256)   Diff: 4/9993