1.
Radzievskii GV. On the best approximations and rate of convergence of decompositions in the root vectors of an operator. Ukr. Mat. Zhurn. [Internet]. 1997Jun.25 [cited 2024Jul.27];49(6):754–773. Available from: https://umj.imath.kiev.ua/index.php/umj/article/view/5060