Dyukarev, Yu. M. “Nevanlinna–Pick Problem for Stieltjes Matrix Functions”. Ukrains’kyi Matematychnyi Zhurnal 56, no. 3 (March 25, 2004): 366-380. Accessed May 3, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/3760.