SAMOILENKO , A. M.; BEREZOVSKY , A. A.; SUYAROV , U. S. School-Seminar «Nonlinear problems of mathematical physics and their applications» . Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 44, n. 5, p. 720, 1992. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/7973. Acesso em: 6 dec. 2025.