Li, Wen-Rong, and Sui Sun Cheng. “Discrete Ou-Iang Type Inequalities”. Tamkang Journal of Mathematics 31, no. 4 (December 31, 2000): 305–310. Accessed April 25, 2024. https://journals.math.tku.edu.tw/index.php/TKJM/article/view/388.