BANG, N. T. On the observable conditions in the nonlinear systems. Vietnam Journal of Mechanics, Hanoi, Vietnam, v. 1, n. 1-2, p. 9–19, 1979. DOI: 10.15625/0866-7136/9888. Disponível em: https://vjs.ac.vn/index.php/vjmech/article/view/9888. Acesso em: 7 may. 2024.