1. University of Wisconsin School of Medicine and Public HealthCenter for Tobacco Research and Intervention Madison WI USA
2. University of Wisconsin School of Medicine and Public HealthDepartment of Medicine Madison WI USA
3. University of WisconsinDepartment of Educational Psychology Madison WI USA
4. The Pennsylvania State UniversityThe Methodology Center and Department of Human Development and Family Studies State College PA USA
5. University of Illinois at ChicagoInstitute for Health Research and Policy Chicago IL USA
6. William S. Middleton Memorial Veterans Hospital Madison WI USA
7. University of WisconsinDepartment of Statistics Madison WI USA