Clinical Features for Severely and Critically Ill Patients with COVID-19 in Shandong: A Retrospective Cohort Study. - Zhou, Shengyu; Xu, Jiawei; Sun, Wenqing; Zhang, Jintao; Zhang, Fayan; Zhao, Xuesong; Wang, Ximing; Zhang, Wei; Li, Yu; Ning, Kang; Pan, Yun; Liu, Tian; et al. (Therapeutics & Clinical Risk Management, 2021)