Principal Eigenvalue for Cooperative (p,q)-biharmonic Systems. Journal of Partial Differential Equations, [S. l.], v. 32, n. 1, p. 33–51, 2019. DOI: 10.4208/jpde.v32.n1.3. Disponível em: https://www.global-sci.com/index.php/jpde/article/view/4320. Acesso em: 6 dec. 2025.