Zhu, Zhi-Qiang, and Sui Sun Cheng. “Asymptotically Power Solutions of Higher Order Neutral Functional Differential Equations”. Tamkang Journal of Mathematics 35, no. 4 (December 31, 2004): 383–389. Accessed July 5, 2022. https://journals.math.tku.edu.tw/index.php/TKJM/article/view/196.