Waqas Saleem and  Fan Yuqing,  Strategy for Optimal Configuration Design of Existing Structures by Topology and Shape Optimization Tools.   journal   = {International Journal of Aerospace and Mechanical Engineering}, [online]. World Academy of Science, Engineering and Technology.
    January 2010, vol. 37(1). 111 - 119
    [viewed 21 January 2020]. Available from: https://publications.waset.org/pdf/13195.