Eke, K. S., B. Davvaz, and J. G. Oghonyon. “Relation-Theoretic Common Fixed Point Theorems for a Pair of Implicit Contractive Maps in Metric Spaces”. Communications in Mathematics and Applications, vol. 10, no. 1, Mar. 2019, pp. 159-68, doi:10.26713/cma.v10i1.873.