H. Praekunatham, S. Buranasatitnon, and H. Ruksakom, “Situation and Spatial Analysis of the COVID-19 Epidemic in Business Establishments: Comparison between the Delta and Omicron Variants in Thailand, July 2021–May 2022”, OSIR, vol. 15, no. 4, pp. 114–122, Dec. 2022.