[1] Zhang,Shi-seng,Fixed Point Theory and Application,Chongqing Press,Chongqing(1984).(in Chinese).
[2] Takahashi,W.,A convexity in metric space and nonexpansive mappings,I.Kodai Math.Sem.Rep.,22(1970),142-149.
[3] Guay,M.D.,K.L.Singh and J.H.M.Whitfield,Fixed point theorems for nonexpansive mappings in convex metric space,Proceedings,Conference on Nonlinear Analysis(Ed.S.P.singh and J.H.Burry)Marcel Dekker,Inc.,New York,80(1982),179-189.
[4] Beg,Ismat and Akbar Azam,(Quaid-i-Azam University,Pakistan)Fixed point theorems for Kannan mappings,Abstracts of International Congress of Mathematicians,Berkeley,California,U.S.A.(1986),3-11.
[5] Kirk,W.A.,A fixed point theorem for mappings which do not increase distances,Amer.Math.Monthly,72(1965),1004-1006.