Multiplicity Results for a Non-Homogeneous Neumann Problem via a Variational Principle of Ricceri. Minimax Theory and its Applications, [S. l.], v. 2, n. 2, p. 249–263, 2017. Disponível em: https://journalmta.com/index.php/jmta/article/view/30. Acesso em: 12 may. 2026.