Domoshnitsky, A., et al. “Semi-Nonoscillation Intervals and Sign-Constancy of Green’s Functions of Two-Point Impulsive Boundary-Value Problems”. Ukrains’kyi Matematychnyi Zhurnal, vol. 73, no. 7, July 2021, pp. 887-01, https://doi.org/10.37863/umzh.v73i7.473.