Furutani, Hiroshi, and Tomoyuki Hiroyasu. “Estimation of COVID-19 Cases in Japanese Prefectures Using a Gumbel Distribution”. Archives of Clinical and Biomedical Research, vol. 6, no. 5, Sept. 2022, pp. 756-63, https://fortunejournals.org/ojs/index.php/acbr/article/view/14955.