“ Solving Systems of Non-Linear Volterra Integral Equations by Combined Sumudu Transform-Adomian Decomposition Method”. Iraqi Journal of Science 62, no. 1 (January 30, 2021): 252–268. Accessed August 8, 2025. https://www.ijs.uobaghdad.edu.iq/index.php/eijs/article/view/2498.