CANDELA, Anna Maria, DE MEDEIROS, Everaldo Souto, PALMIERI, Giuliana and PERERA, Kanishka. Weak solutions of quasilinear elliptic eystems via the cohomological index. Topological Methods in Nonlinear Analysis. Online. 23 April 2010. Vol. 36, no. 1, pp. 1 - 18. [Accessed 22 July 2024].