Variations on Advanced Sudoku Logic Puzzles (Vol 1) 
 Chapter 34: Four Medium Sudoku-15up Puzzles (numbers 111-114) 
 
-  Step-by-step instructions for solving  Puzzle 111, (117/225)   Diff: 6/99.9995
 -  Step-by-step instructions for solving  Puzzle 112, (102/225)   Diff: 7/999.6642
 -  Step-by-step instructions for solving  Puzzle 113, (114/225)   Diff: 8/9999.9996
 -  Step-by-step instructions for solving  Puzzle 114, (119/225)   Diff: 8/9999.9994