Oelsner EC, Krishnaswamy A, Rustamov R, et al. Classifying COVID-19 hospitalizations in epidemiology cohort studies: The C4R study. PloS one. 2025;20(2):e0316198. doi:10.1371/journal.pone.0316198

Balte PP, Kim JS, Sun Y, et al. Associations of Prepandemic Lung Function and Structure with COVID-19 Outcomes: The C4R Study. American journal of respiratory and critical care medicine. 2025;211(7):1196-1210. doi:10.1164/rccm.202408-1656OC

Oelsner EC, Krishnaswamy A, Balte PP, et al. Collaborative Cohort of Cohorts for COVID-19 Research (C4R) Study: Study Design. Am J Epidemiol. 2022;191(7):1153-1173. doi:10.1093/aje/kwac032