Sudoku Strategy: Using Number Sets to Solve Difficult Puzzles Mentally

Tools to solve difficult Sudoku puzzles mentally without pen & paper. Most Sudoku strategies rely upon deductive reasoning which requires keeping track of a large number of possible solutions for each open cell. These strategies enable even inexperienced players to solve difficult puzzles using only a few numbers (usually two, three or four) at a time. It includes step-by-step solutions to several puzzles.