Gutik, O. V. and Zarichnyi, M. M. (2006) “Еhird summer school algebra, analysis and topology”, Ukrains’kyi Matematychnyi Zhurnal, 58(2), pp. 288-289. Available at: https://umj.imath.kiev.ua/index.php/umj/article/view/3453 (Accessed: 2December2022).