XUN GE; JINGYU QIAN. A fixed point theorem for contractive closed-valued mappings on metric spaces. Scientia Series A: Mathematical Sciences, [S. l.], v. 16, p. 105–108, 2008. DOI: 10.71712/. Disponível em: https://revistas.usm.cl/scientia/article/view/114.. Acesso em: 7 jun. 2025.