References
- Thomas Butts, Problem Solving in Mathematics: Elementary Number Theory and Arithmetic, Scott, Foresman, Glenview, IL, 1973; pp. 4–5.
- John Mason, Leone Burton, and Kaye Stacey, Thinking Mathematically, Addison-Wesley, London, 1982: pp. 76–84.
- George Pólya, Induction and Analogy in Mathematics, vol. 1, Princeton, 1954; pp. 45–52.