John Xu , Zhi-QinZhang , YaoyuLuo , TaoXiao , Yanyang and Ma , Zheng. (2020). Frequency Principle: Fourier Analysis Sheds Light on Deep Neural Networks.
            <i>Communications in Computational Physics</i>. <i>28</i> (5).
            1746-1767.
         doi:10.4208/cicp.OA-2020-0085