Kalemba, Piotr, and Andrzej Kucharski. “Universally Kuratowski–Ulam Spaces and Open-Open Games”. Annales Mathematicae Silesianae 29 (September 30, 2015): 85-92. Accessed May 17, 2024. https://www.journals.us.edu.pl/index.php/AMSIL/article/view/13979.