Babenko, V. F., and M. E. Tkachenko. “Problem of Uniqueness of an Element of the Best Nonsymmetric <i>L</i><sub> 1</sub>-Approximation of Continuous Functions With Values in <i>KB</I&gt; -Spaces”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 60, no. 7, July 2008, pp. 867 -, https://umj.imath.kiev.ua/index.php/umj/article/view/3205.