Chapovsky, Yu., and A. A. Kalyuzhnyi. “Factorization of Conditional Expectations on Kac Algebras and Quantum Double Coset Hypergroups”. Ukrains’kyi Matematychnyi Zhurnal 55, no. 12 (December 25, 2003): 1669-1677. Accessed May 28, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/4029.