DAVYDOV, N. A. Two theorems in the theory of summation of numerical series by lower triangular positive monotone matrices. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 51, n. 4, p. 553–555, 1999. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/4639. Acesso em: 6 dec. 2025.