S. . BENSLIMANE, S. G. . GEORGIEV, and K. . MEBARKI, “Expansion-compression fixed point theorem of Leggett-Williams type for the sum of two operators and applications for some classes of BVPs”, Stud. Univ. Babeş-Bolyai Math., vol. 68, no. 3, pp. 631–647, Sep. 2023.