Zabolotskii, N. V., and M. R. Mostova. 2016. “Sufficient Conditions for the Existence of the $\upsilon$ -Density for Zeros of Entire Function of Order Zero”. Ukrains’kyi Matematychnyi Zhurnal 68 (4), 506-16. https://umj.imath.kiev.ua/index.php/umj/article/view/1856.