Ivany, Sara, and Reza Jalilian. 2023. “Trigonometric Spline Method for the Numerical Solutions of Singularly Perturbed Volterra Integro-Differential Equations”. Thai Journal of Mathematics 21 (2):299–314. https://thaijmath2.in.cmu.ac.th/index.php/thaijmath/article/view/1460.