“On the rate of convergence of the sum of the squares of the $s$-values of the integral Hilbert - Schmidt’s operator”, НК, vol. 2, no. 3, pp. 384–390, Sep. 1999, Accessed: Jan. 22, 2026. [Online]. Available: https://twinhead.imath.kiev.ua/index.php/nosc/article/view/73