Ang Li, Xiaofeng Hu, Zhaolong Zeng, Huanggang Wu, Jie Gao. “Risk Analysis of Intergroup Conflicts under the COVID-19 Pandemic: A Case Study of Washington, DC”. Design Engineering, Dec. 2020, pp. 397 -14, http://thedesignengineering.com/index.php/DE/article/view/1090.