OlatinwoM. O. “Some Generalizations of Non-Unique Fixed Point Theorems of Ćirić-Type for (Φ,ψ)-Hybrid Contractive Mappings”. Annales Mathematicae Silesianae, Vol. 33, June 2019, pp. 221-34, https://www.journals.us.edu.pl/index.php/AMSIL/article/view/13669.