Nyein, E. E., and A. Khaing Zaw. “Quasi (s,r)-Contractive Multi-Valued Operators on B-Metric Space and Related Fixed Point Theorems”. Journal of the Indonesian Mathematical Society, vol. 26, no. 3, Nov. 2020, pp. 393-02, doi:10.22342/jims.26.3.941.393-402.