A. Barbir, . K. . K. Himmelreich, and J. E. Pečarić, “Refinements of Jessen’s functional”, Ukr. Mat. Zhurn., vol. 68, no. 7, pp. 879–896, Jul. 2016, Accessed: Dec. 05, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/1888