SAVCHUK, V. V.; SAMOILENKO, A. M.; SOKOLENKO, I. V.; STEPANETS, O. I. International Conference "Mathematical Analysis and Differential Equations and Applications". Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 59, n. 3, p. 431, 2007. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/3317. Acesso em: 11 apr. 2025.