1. University of North Carolina School of Medicine, Chapel Hill, North Carolina, USA.
2. UNC Health Sciences Library, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA.
3. Gillings School of Public Health, University of North Carolina, Chapel Hill, North Carolina, USA.
4. Department of Population Health Sciences, Duke University School of Medicine, Durham, North Carolina, USA.
5. Department of Surgery, University of North Carolina School of Medicine, Chapel Hill, North Carolina, USA.