BOYADZHIEV, G. Comparison principle for linear non-cooperative elliptic systems. Ann. Sofia Univ. Fac. Math. and Inf., [S. l.], v. 99, p. 111–119, 2009. Disponível em: https://stipendii.uni-sofia.bg/index.php/fmi/article/view/115. Acesso em: 4 dec. 2024.