Aldanov, V. M., and G. A. Mikhalin. 1999. “Tauberian Theorems With Remainder for (H, P, α, β)-and (C, P, α, β)-Methods of Summation of Functions of Two Variables”. Ukrains’kyi Matematychnyi Zhurnal 51 (8): 1036–1044. https://umj.imath.kiev.ua/index.php/umj/article/view/4694.