1. Ball, W.W.R. 1959. “Mathematical Recreations and Essays”. London: Macmillan & Co.
2. 3918
3. Pascal's Triangle and the Tower of Hanoi
4. Papadimitriou, C.H. and Steiglitz, K. 1982. “Combinatorial Optimization”. Eaglewood Cliffs, N.J: Prentice-Hall.
5. Reingold, E.M. and Hansen, W.J. 1983. “Data Structures. Little Brown Computer Systems Series”. N.Y