1. Centers for Disease Control and Prevention. CDC COVID data tracker. CDC; Access Date: October 2020.
2. The COVID Tracking Project. National: hospitalization. The atlantic monthly group; Access Date: October 2020.
3. Gasparini A. Comorbidity Scores. The Comprehensive R Archive Network. Institute for Statistics and mathematics of WU; Access Date: September 2020.
4. Transparent reporting of a multivariable prediction model for individual prognosis or diagnosis (TRIPOD);Collins;Ann Intern Med,2015
5. Prediction of hospital length of stay;Robinson;Health Serv Res,1966