ErgörenH. “Impulsive Functional Differential Equations of Fractional Order With Variable Moments”. Ukrains’kyi Matematychnyi Zhurnal 68, no. 9 (September 25, 2016): 1169-1179. Accessed November 29, 2020. http://umj.imath.kiev.ua/index.php/umj/article/view/1912.