ANH, Nguyen Dong; KHIEM, Nguyen Tien. Non-linear oscillations in first order systems with delay. II. Non-autonomous case. <b>Vietnam Journal of Mechanics</b>, Hanoi, Vietnam, v. 12, n. 3, p. 1–7, 1990. DOI: 10.15625/0866-7136/10282. Disponível em: https://vjmech.vast.vn/vjmech/article/view/10282. Acesso em: 9 nov. 2025.