altaher, ahsan, and Hameeda Oda Al-Humedi. 2020. “ A Combination of the Orthogonal Polynomials With Least – Squares Method for Solving High-Orders Fredholm-Volterra Integro-Differential Equations”. Al-Qadisiyah Journal of Pure Science 26 (1), Math 20-38. https://doi.org/10.29350/qjps.2021.26.1.1207.