Hua Tang, Xianzheng Zong, and Zaiping Nie. “On the Approximate Calculation of Half-Power Beam Width for Uniform Circular Arrays”. The Applied Computational Electromagnetics Society Journal (ACES), vol. 34, no. 03, Mar. 2019, pp. 444-50, https://journals.riverpublishers.com/index.php/ACES/article/view/8563.