Dzyubenko, H. A. “Pointwise Estimation of an Almost Copositive Approximation of Continuous Functions by Algebraic Polynomials”. Ukrains’kyi Matematychnyi Zhurnal 69, no. 5 (May 25, 2017): 641–649. Accessed April 7, 2025. https://umj.imath.kiev.ua/index.php/umj/article/view/1723.