GUSAK, D. V. Conditions for balance between survival and ruin. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 64, n. 7, p. 988–993, 2012. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/2633. Acesso em: 5 dec. 2025.