KU, H.-T.; KU, M.-C.; ZHANG, X.-M. EIGENVALUE ESTIMATES FOR HIGHER ORDER ELLIPTIC EQUATIONS. Tamkang Journal of Mathematics, [S. l.], v. 25, n. 3, p. 267–278, 1994. DOI: 10.5556/j.tkjm.25.1994.4454. Disponível em: https://journals.math.tku.edu.tw/index.php/TKJM/article/view/4454. Acesso em: 3 may. 2024.