On the Accuracy and Efficiency of Galerkin and Direct Methods for Second-Order Boundary Value Problems with Neumann Boundary Conditions. Pi International Journal of Mathematical Sciences, [S. l.], v. 2, n. 2, p. 1–7, 2026. DOI: 10.59828/pijms.v2i2.29. Disponível em: https://pijms.com/index.php/pijms/article/view/29. Acesso em: 7 may. 2026.