Vishki, H. R., and A. Jabbari. “A Class of Distal Functions on Semitopological Semigroups”. Methods of Functional Analysis and Topology 15, no. 2 (June 25, 2009): 188–194. Accessed December 16, 2025. https://zen.imath.kiev.ua/index.php/mfat/article/view/418.