1. Department of Research and Evaluation, Legacy, Washington, DC 20036, USA
2. The Schroeder Institute for Tobacco Research and Policy Studies, Legacy, Washington, DC 20036, USA
3. Department of Health, Behavior and Society, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA
4. Department of Oncology, Georgetown University Medical Center and Lombardi Comprehensive Cancer Center, Washington, DC 20007, USA