Banakh, T. O., and Radyl Т. “On Universality of Countable Powers of Absolute Retracts”. Ukrains’kyi Matematychnyi Zhurnal 48, no. 4 (April 25, 1996): 540–542. Accessed April 11, 2025. https://umj.imath.kiev.ua/index.php/umj/article/view/5317.