DAVYDOV, N. A. On necessary and sufficient conditions for the summability of a numerical series to imply its convergence. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 47, n. 6, p. 747–754, 1995. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/5467. Acesso em: 6 dec. 2025.