NGUYEN VAN DUNG. \(ls\)-Ponomarev-systems and 1-sequence-covering mappings. Scientia Series A: Mathematical Sciences, [S. l.], v. 19, p. 25–36, 2010. DOI: 10.71712/. Disponível em: https://revistas.usm.cl/scientia/article/view/136.. Acesso em: 6 jun. 2025.