Mozel’, V. A. “On a Banach Algebra Generated by the Bergman Operator, Constant Coefficients, and Finitely Generated Groups of Shifts”. Ukrains’kyi Matematychnyi Zhurnal, vol. 69, no. 11, Nov. 2017, pp. 1515-23, https://umj.imath.kiev.ua/index.php/umj/article/view/1799.