Rynne, Bryan P. “Eigenvalue Criteria for Existence of Positive Solutions of Second-Order, Multi-Point, $p$-Laplacian Boundary Value Problems”. Topological Methods in Nonlinear Analysis 36, no. 2 (April 23, 2010): 311–326. Accessed January 17, 2022. https://apcz.umk.pl/TMNA/article/view/TMNA.2010.038.