Mozel’V. A. “Banach Algebra Generated by a Finite Number of Bergman Polykernel Operators, Continuous Coefficients, and a Finite Group of Shifts”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 62, no. 9, Sept. 2010, pp. 1247–1255, https://umj.imath.kiev.ua/index.php/umj/article/view/2951.