1. M. Edelstein, On fixed and periodic points under contractive mappings. J. London Math. Soc.37, 74?79 (1962).
2. R. Kannan, Some results on fixed points. Bull. Calcutta Math. Soc.60, 71?76 (1968).
3. R. Kannan, Some results on fixed points II. Amer. Math. Monthly76, 405?408 (1969).
4. S. P. Singe, Some theorems on fixed points. Yokohama Math. J.18, 23?25 (1970).