Annas, Suwardi, et al. “Determinants of Maternal Mortality in Indonesia: A B-Spline Nonparametric Regression Approach to Identify Nonlinear Relationship Patterns”. Mathline : Jurnal Matematika Dan Pendidikan Matematika, vol. 11, no. 1, Feb. 2026, pp. 31-44, doi:10.31943/mathline.v11i1.1015.