SOTNICHENKO, N. A. Asymptotics of solutions of à system of differential equations with “turning points”. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 48, n. 6, p. 861–862, 1996. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/5288. Acesso em: 5 dec. 2025.