Gasiński, Leszek, and Nikolaos S. Papageorgiou. “Multiple Solutions for Nonlinear Dirichlet Problems With Concave Terms”. MATHEMATICA SCANDINAVICA 113, no. 2 (December 1, 2013): 206–247. Accessed August 14, 2026. https://tidsskrift.dk/math/article/view/15570.