Qin, Qin, Liwei Cheng, Li Tan, Yunzhou Fan, Li Liu, Lihong Tian, Ying Wang, et al. “Over-the-Counter Medication Sales Surveillance for Early Detection of Respiratory Epidemics in Rural China”. Online Journal of Public Health Informatics 6, no. 1 (March 9, 2014). Accessed April 19, 2024. https://ojphi.org/ojs/index.php/ojphi/article/view/5144.