Domoshnitsky, A., Iu. Mizgireva, and V. Raichik. “Semi-Nonoscillation Intervals and Sign-Constancy of Green’s Functions of Two-Point Impulsive Boundary-Value Problems”. Ukrains’kyi Matematychnyi Zhurnal 73, no. 7 (July 20, 2021): 887 - 901. Accessed August 12, 2022. http://umj.imath.kiev.ua/index.php/umj/article/view/473.