Nomogram to identify severe coronavirus disease 2019 (COVID-19) based on initial clinical and CT characteristics: a multi-center study. - Yixing Yu; Ximing Wang; Min Li; Lan Gu; Zongyu Xie; Wenhao Gu; Feng Xu; Yaxing Bao; Rongrong Liu; Su Hu; Mengjie Hu; Chunhong Hu (BMC Medical Imaging, 2020)