Bai, Liang, and Juan J. Nieto. “Positive Solutions for Singular Impulsive Dirichlet Boundary Value Problems”. Topological Methods in Nonlinear Analysis 52, no. 2 (November 3, 2018): 561–584. Accessed March 29, 2024. https://apcz.umk.pl/TMNA/article/view/TMNA.2018.017.