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 November 22, 2024. https://www.mscand.dk/article/view/15570.