In this paper, an elliptic system with sign-changing weights is considered. By variational methods, we show that the problem has at least three nontrivial solutions.
Huyuan Chen. Jianfu Yang. "Multiple solutions for nonlinear elliptic systems with changing-sign weights." Differential Integral Equations 22 (3/4) 239 - 250, March/April 2009. https://doi.org/10.57262/die/1356019772