BanakhT. O., and LyaskovskaN. “Completeness of Invariant Ideals in Groups”. Ukrains’kyi Matematychnyi Zhurnal 62, no. 8 (August 25, 2010): 1022–1031. Accessed July 27, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/2934.