The Ultraconvergence of Eigenvalues for Bi-Quadratic Finite Elements. Journal of Computational Mathematics, [S. l.], v. 30, n. 5, p. 555–564, 2018. DOI: 10.4208/jcm.1203-m3977. Disponível em: https://www.global-sci.com/index.php/JCM/article/view/12094. Acesso em: 6 dec. 2025.