PTASHNIK, B. I.; SAMOILENKO, A. M. International scientific conference "New approaches to the solution of differential equations". Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 54, n. 4, p. 575–576, 2002. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/4095. Acesso em: 5 dec. 2025.