O. O. Karlova and V. V. Mykhailyuk, “Cross Topology and Lebesgue Triples”, Ukr. Mat. Zhurn., vol. 65, no. 5, pp. 722–727, May 2013, Accessed: Dec. 05, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/2456