ProtasovI. V. and SlobodianiukS. V. (2015) “Ultrafilters on balleans”, Ukrains’kyi Matematychnyi Zhurnal, 67(12), pp. 1698-1706. Available at: https://umj.imath.kiev.ua/index.php/umj/article/view/2102 (Accessed: 1September2024).