“…Some of them used Banach, Leray-Schauder, Krasnoselskii fixed point theorems, and the Banach contraction mapping principle. Several researchers worked by applying the Krein-Rutman theorem, fixed point theorem of Darbo-type, and Lyapunov-type inequality, to know more, see the studies [22,23,24,25,26,27] and references therein.…”