IvashchukO. V., ZadereiP. V., and PelagenkoE. N. 2008. “On Sidon-Telyakovskii-Type Conditions for the Integrability of Multiple Trigonometric Series”. Ukrains’kyi Matematychnyi Zhurnal 60 (5), 579–585. https://umj.imath.kiev.ua/index.php/umj/article/view/3177.