BanduraA. I., and SkaskivO. B. “Boundedness of $l$-Index and Completely Regular Growth of Entire Functions”. Ukrains’kyi Matematychnyi Zhurnal 72, no. 3 (March 28, 2020): 316-325. Accessed January 19, 2021. http://umj.imath.kiev.ua/index.php/umj/article/view/1048.