1. The determination of Kaprekar convergence and loop convergence of all three-digit numbers;Eldridge;Amer. Math. Monthly,1988
2. The determination of all four-digit Kaprekar constants;Hasse;J. Reine Angew. Math.,1978
3. Self-producing sequences of digits;Jordan;Amer. Math. Monthly,1964
4. Another solitaire game;Kaprekar;Scr. Math.,1949
5. An interesting property of the number 6174;Kaprekar;Scr. Math.,1955