3000 Sudoku: Suduko Puzzle Book for Adults with Hard to Extreme Hard Puzzles: visugames: 9798665156422: Amazon.com: Books
Sudoku Next Level 320 Hard Puzzles: Perfect Hard Sudoku Puzzle Book for anyone that needs to be tested: Genius, Puzzlebook101: 9798662819412: Amazon.com: Books
Binary puzzle book for Adults: 400 Very Hard Puzzles Mixed Grids (Volume 26): Gurin, Alena: 9798722142894: Amazon.com: Books
Hardest Puzzles You Can Get on Amazon | Reader's Digest
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Tatami Puzzle Book 2: 200 Hard Puzzles: Quinlan, Kenneth, Publishing, WMC: 9781660916795: Amazon.com: Books
Amazon.com: Maths Hard Puzzles With Answers: Calcudoku 9x9 Puzzles (Adult Logic Puzzle Book): 9781723979682: White, Marcus: Books
501 Really Hard Sudoku Puzzles: Jones, Louise: 9781933819884: Amazon.com: Books
Amazon.com: Word Search - Hard Level: Large Print Word Search Puzzle Book for Adults, Word Find Puzzles, 100 Word Puzzles: 9781657141568: Emma Byron: Books
Tapa puzzle book for Adults: 400 Medium to Hard Puzzles 9x9 (Volume 15): Gurin, Alena: 9798730220539: Amazon.com: Books
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Best Logic Puzzles: 500 Easy to Hard Puzzles & 12 Puzzle Types (Sudoku, Fillomino, Battleships, Calcudoku, Binary Puzzle, Slitherlink, Sudoku X, ... Suguru, and Numbrix) (Puzzles Books Series): Alzamili, Dr. Khalid: 9789922636238: Amazon.com: Books
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B is for Brainy Sudoku: 200 Large Print Easy to Hard Puzzles (A-Z Sudoku Book Series): Gruden, Lou, Plus, Puzzle Books: 9798985346923: Amazon.com: Books
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SUDOKU: 100 Hard Puzzles (Sudoku Puzzles): Pals, Puzzle, Ross, Bryce: 9781704189505: Amazon.com: Books
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Puzzle Wild Sudoku 1000+ Puzzles Easy To Hard Series One (Puzzle Wild 1000 Series): Wild, P: 9798734500958: Amazon.com: Books
200 HARD Sudoku puzzles with answers for those long summer days: Brain training puzzles for children to adults - Vol 1: Birch, Kevin, Addicts, Puzzle: 9781076710826: Amazon.com: Books
