books.google.com - All the puzzles in the three volumes of Super Sudoku are collected in this single edition. A total of 228 puzzles from easy to hard (levels 1-6)....https://books.google.com/books/about/Super_Sudoku_Fusion.html?id=1as_Hgl6m3MC&utm_source=gb-gplus-shareSuper Sudoku Fusion
James E. Riley, PhD, was a professor of mathematics at Western Michigan University and a high school math teacher for 30 years after serving as an officer in the U.S. Army. His previous books include Helping Your Child with Math, Stand Up Math and Middle School Math Competition Problems. He currently resides in Teddington, England.