Оvsepyan K. H. “Type of Some Nuclear Subalgebras of the Toeplitz Algebra Generated by the Inverse Subsemigroups of a Bicyclic Semigroup”. Ukrains’kyi Matematychnyi Zhurnal 69, no. 11 (November 25, 2017): 1551–1563. Accessed December 5, 2025. https://umj.imath.kiev.ua/index.php/umj/article/view/1802.