La Rosa, Vincenzo, and Pasquale Vetro. “On Fixed Points for for alpha–eta–psi-Contractive Multi-Valued Mappings in Partial Metric Spaces”. Nonlinear Analysis: Modelling and Control 20, no. 3 (July 20, 2015): 377–394. Accessed May 6, 2024. https://www.journals.vu.lt/nonlinear-analysis/article/view/13521.