5x5 Sudoku: For Beginners Vol.1: 200 Easy Sudoku Puzzles For Teens & Adults: Thomas, Christopher: 9781721715138: Amazon.com: Books
Chain Sudoku Ser.: Puzzles for Brain - Chain Sudoku 200 Hard to Expert Puzzles 5x5 Vol. 2 by Alexander Rodriguez (2018, Trade Paperback) for sale online | eBay