1. Tobacco Control Research Branch, Division of Cancer Control and Population Sciences, National Cancer Institute, Bethesda, MD 20892, USA
2. American Cancer Society, Atlanta, GA 30303, USA
3. Office on Smoking and Health, National Center for Chronic Disease Prevention and Health Promotion, Centers for Disease Control and Prevention, Atlanta, GA 30333, USA
4. BLH Technologies, Inc., Rockville, MD 20850, USA
5. Westat, Rockville, MD 20850, USA