Kalchuk IV, Kharkevych YI. Asymptotics of the values of approximations in the mean for classes of differentiable functions by using biharmonic Poisson integrals. Ukr. Mat. Zhurn. [Internet]. 2007Aug.25 [cited 2024May7];59(8):1105–1115. Available from: https://umj.imath.kiev.ua/index.php/umj/article/view/3373