ZhelnovO. D. “Whitney Interpolation Constants Bounded by 2 for <em class="a-Plus-plus">k</Em&gt; = 5, 6, 7”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 55, no. 4, Apr. 2003, pp. 546-9, https://umj.imath.kiev.ua/index.php/umj/article/view/3928.