O'RIORDAN, E.; PICKETT, M. L.; SHISHKIN, G. I. Numerical methods for singularly perturbed elliptic problems containing two perturbation parameters. Mathematical Modelling and Analysis, [S. l.], v. 11, n. 2, p. 199–212, 2006. DOI: 10.3846/13926292.2006.9637313. Disponível em: https://journals.vilniustech.lt/index.php/MMA/article/view/9611. Acesso em: 2 jun. 2025.