“Pointwise Estimates for Finding the Error of Best Approximation by Spline, Positive Algebraic Polynomials and Copositive”. Iraqi Journal of Science 63, no. 11 (November 30, 2022): 4967–4986. Accessed May 2, 2024. https://ijs.uobaghdad.edu.iq/index.php/eijs/article/view/6802.