Slyusarchuk, V. Yu. “Conditions for the Existence of Almost Periodic Solutions of Nonlinear Differential Equations in Banach Spaces”. Ukrains’kyi Matematychnyi Zhurnal, vol. 65, no. 2, Feb. 2013, pp. 307-12, https://umj.imath.kiev.ua/index.php/umj/article/view/2420.