Mulyava, O. M., and M. M. Sheremeta. 2008. “On Conditions for Dirichlet Series Absolutely Convergent in a Half-Plane to Belong to the Class of Convergence”. Ukrains’kyi Matematychnyi Zhurnal 60 (6), 851–856. https://umj.imath.kiev.ua/index.php/umj/article/view/3202.