Wei, Fengtao, Dexiao Kong, Tao Li, Ai Li, Yi Tan, Jinfeng Fang, Xianghua Zhuang, et al. 2021. “Efficacy and Safety of Umbilical Cord Mesenchymal Stem Cells for the Treatment of Patients With COVID-19”. Clinics 76 (November): e2604. https://doi.org/10.6061/clinics/2021/e2604.