Vestfrid, I. A. 2001. “Isometric Imbedding of Some Metric Spaces in l<sub class="a-Plus-plus">p</Sub&gt;-Spaces”. Ukrains’kyi Matematychnyi Zhurnal 53 (12), 1718-23. https://umj.imath.kiev.ua/index.php/umj/article/view/4389.