Berestycki, H., Capuzzo Dolcetta, I., & Nirenberg, L. (1994). Superlinear indefinite elliptic problems and nonlinear Liouville theorems. Topological Methods in Nonlinear Analysis, 4(1), 59–78. Retrieved from https://apcz.umk.pl/TMNA/article/view/TMNA.1994.023