1. Division of Cancer Epidemiology and Genetics; National Cancer Institute; Rockville Maryland
2. Department of Epidemiology, Human Genetics, and Environmental Sciences, The University of Texas School of Public Health; Houston Texas
3. Department of Infectious Diseases, Infection Control, and Employee Health; The University of Texas MD Anderson Cancer Center; Houston Texas
4. Center for Innovations in Quality, Effectiveness, and Safety; Michael E. DeBakey Veterans Affairs Medical Center; Houston Texas
5. Department of Biostatistics; The University of Texas School of Public Health; Houston Texas