1. Danesi, Marcel: The Puzzle Instinct: the meaning of puzzles in human life. Indiana University Press, Bloomington, IN (2002)
2. Haley, Alex: Roots. Doubleday, New York (1976)
3. Movshovitz-Hadar, N., Webb, J.: One Equals Zero and Other Mathematical Surprises. Key Curriculum Press, Berkeley, CA (1998)