Kholshchevnikova Н. . “Sets of Uniqueness for Regular Methods of Summation”. Bulletin of L.N. Gumilyov Eurasian National University. Mathematics, Computer Science, Mechanics Series, vol. 125, no. 4, Dec. 2018, pp. 113-6, https://bulmathmc.enu.kz/index.php/main/article/view/37.