Weikang Yu, Hu Yang, Shengguo Li, and Yanlin Xu. “An HSS-Matrix-Based Fast Direct Solver With Randomized Algorithm”. The Applied Computational Electromagnetics Society Journal (ACES), vol. 33, no. 07, July 2021, pp. 814-7, https://journals.riverpublishers.com/index.php/ACES/article/view/9091.