MulyavaO. M., and SheremetaM. M. “On Conditions for Dirichlet Series Absolutely Convergent in a Half-Plane to Belong to the Class of Convergence”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 60, no. 6, June 2008, pp. 851–856, https://umj.imath.kiev.ua/index.php/umj/article/view/3202.