Pourhadi, Ehsan, et al. “Some Krasnosel’skii-Type Fixed Point Theorems for Meir–Keeler-Type Mappings”. Nonlinear Analysis: Modelling and Control, vol. 25, no. 2, Mar. 2020, pp. 257–265, https://doi.org/10.15388/namc.2020.25.16516.