CHENG, S. S. LYAPUNOV INEQUALITY FOR SYSTEM DISCONJUGACY OF EVEN ORDER DIFFERENTIAL EQUATIONS. Tamkang Journal of Mathematics, [S. l.], v. 22, n. 2, p. 193–197, 1991. DOI: 10.5556/j.tkjm.22.1991.4598. Disponível em: https://journals.math.tku.edu.tw/index.php/TKJM/article/view/4598. Acesso em: 29 apr. 2024.