ZHELTUKHINA, N. On power series whose tails have multiply positive coefficients. Математическая физика, анализ, геометрия, Харків, Україна, v. 10, n. 2, p. 156–166, 2003. Disponível em: https://mag.ilt.kharkiv.ua/index.php/mag/article/view/m10-0156e. Acesso em: 4 груд. 2024.