Slyusarchuk, V. Yu. “Conditions of Existence of Bounded and Almost Periodic Solutions of Nonlinear Differential Equation With Perturbations of Solutions”. Ukrains’kyi Matematychnyi Zhurnal, vol. 68, no. 9, Sept. 2016, pp. 1286-9, https://umj.imath.kiev.ua/index.php/umj/article/view/1921.