Pointwise Estimates for Finding the Error of Best Approximation by Spline, Positive Algebraic Polynomials and Copositive. Iraqi Journal of Science [Internet]. 2022 Nov. 30 [cited 2024 May 2];63(11):4967-86. Available from: https://ijs.uobaghdad.edu.iq/index.php/eijs/article/view/6802