Zhengfang Zhang,  Yanqiang Dong & Weifeng Chen. (2021). A Non-Ersatz Material Approach for the Topology Optimization of Elastic Structures Based on Piecewise Constant Level Set Method.
            <i>Communications in Computational Physics</i>. <i>30</i> (5).
            1370-1389.
         doi:10.4208/cicp.OA-2020-0231