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 September 28, 2022. http://umj.imath.kiev.ua/index.php/umj/article/view/1723.