Xu, Yong, Dongli Chen, and Dongli Chen. “The Landau Problem for Univalent Bounded Nonvanishing Functions”. Tamkang Journal of Mathematics 35, no. 2 (June 30, 2004): 101-104. Accessed May 26, 2022. https://journals.math.tku.edu.tw/index.php/TKJM/article/view/210.