Chyzhykov., I. E. “On a Complete Description of the Class of Functions Without Zeros Analytic in a Disk and Having Given Orders”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 59, no. 7, July 2007, pp. 979–995, https://umj.imath.kiev.ua/index.php/umj/article/view/3360.