SI, Nguyen Thac. On modal analysis of mechanical systems. <b>Vietnam Journal of Mechanics</b>, Hanoi, Vietnam, v. 10, n. 2, p. 21–24, 1988. DOI: 10.15625/0866-7136/10326. Disponível em: https://vjs.ac.vn/vjmech/article/view/10326. Acesso em: 5 dec. 2025.