PopovichevaT. N. and KhlobystovV. V. (2006) “On interpolation approximation of differentiable operators in a Hilbert space”, Ukrains’kyi Matematychnyi Zhurnal, 58(4), pp. 554–563. Available at: https://umj.imath.kiev.ua/index.php/umj/article/view/3473 (Accessed: 25November2024).