JEGOROVS, J.; MOHRING, J. A third order correction to the Helmholtz equation. Mathematical Modelling and Analysis, [S. l.], v. 10, n. 1, p. 51–62, 2005. DOI: 10.3846/13926292.2005.9637270. Disponível em: https://journals.vilniustech.lt/index.php/MMA/article/view/9662. Acesso em: 9 may. 2025.