Easy Sudoku Twelve Logic Puzzles (Vol 1) 
 Chapter 49: Two Easy (DiffLev 3-4) Turbomachine Puzzles (numbers 177-178) 
 
-  Step-by-step instructions for solving  Puzzle 177, (55/144)   Diff: 3/991
 -  Step-by-step instructions for solving  Puzzle 178, (71/144)   Diff: 4/9993