ANH, N. D.; KHIEM, N. T. Oscillations in the first order non-linear systems with delay. I. Autonomous systems. Vietnam Journal of Mechanics, Hanoi, Vietnam, v. 12, n. 2, p. 1–5, 1990. DOI: 10.15625/0866-7136/10277. Disponível em: https://vjs.ac.vn/index.php/vjmech/article/view/10277. Acesso em: 20 apr. 2024.