Hnatyuk, Yu. V. “The Best Uniform Approximation in the Metric Space of Continuous Maps With Compact Convex Images”. Ukrains’kyi Matematychnyi Zhurnal, vol. 62, no. 12, Dec. 2010, pp. 1620-33, https://umj.imath.kiev.ua/index.php/umj/article/view/2987.