Fourth-Order Compact Schemes for Helmholtz Equations with Piecewise Wave Numbers in the Polar Coordinates. Journal of Computational Mathematics, [S. l.], v. 34, n. 5, p. 499–510, 2018. DOI: 10.4208/jcm.1604-m2015-0290. Disponível em: https://www.global-sci.com/index.php/JCM/article/view/12244. Acesso em: 5 dec. 2025.