MaimeskulV. V. “Estimates of the Growth of Conjugated Harmonic Polynomials in the Regions of a Complex Plane ”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 42, no. 6, June 1990, pp. 772-7, https://umj.imath.kiev.ua/index.php/umj/article/view/8834.