1. Transformazioni di tipo contracttivo generalizzato in uno spazio metrico;Bianchini;Atti Acad. Naz. Lincei, VII. Ser. Rend. Cl. Sci. Fis. Mat. Natur.,1968
2. Generalized Contractions and Applications;Rus,2001
3. A generalization of Banach’s contraction principle;Ćirić;Proc. Am. Math. Soc.,1974
4. Some Remarks Concerning Contraction Mappings
5. Some results on fixed points;Kannan;Bull. Calcutta Math. Soc.,1968