1. A generalization of Wythoff's game
2. G. H. Hardy and E. M. Wright, An Introduction to the Theory of Numbers, Oxford University Press, 4th ed., 1960.
3. D. E. Knuth, The Art of Computer Programming, vol. 1; Fundamental Algorithms, Addison-Wesley, Reading, MA, second printing, 1969.
4. C. D. Olds, Continued Fractions, Random House, New York, 1963.