POPOVICHEVA, T. N.; KHLOBYSTOV, V. V. On interpolation approximation of differentiable operators in a Hilbert space. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 58, n. 4, p. 554–563, 2006. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/3473. Acesso em: 6 dec. 2025.