Treatment effect of Qingfei Paidu decoction combined with conventional treatment on COVID-19 patients and other respiratory diseases: A multi-center retrospective case series - Zong, X; Liang, N; Wang, J; Li, H; Wang, D; Chen, Y; Zhang, H; Jiao, L; Li, A; Wu, G; Li, J; Wang, M; Liu, H; Liu, Z; Zhao, S; Huang, J; Huang, Q; Wang, X; Qin, J; Ma, Y; Wang, Y; Shi, N (Front Pharmacol, 2022)