StepanecA., and RomanyukV. “Classes of $(\psi, \beta)$-Differential Functions of Complex Variable and Approximation by Linear Averages of Their Faber Series ”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 44, no. 11, Nov. 1992, pp. 1556-70, https://umj.imath.kiev.ua/index.php/umj/article/view/8259.