Liu, Zhenhai, and Nikolaos S. Papageorgiou. “Singular Anisotropic Equations With a Sign-Changing Perturbation”. Nonlinear Analysis: Modelling and Control 28, no. 6 (October 27, 2023): 1120–1137. Accessed February 2, 2026. https://www.journals.vu.lt/nonlinear-analysis/article/view/33472.