1. Center for Tobacco Research and InterventionUniversity of Wisconsin School of Medicine and Public Health 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 Methodology CenterThe Pennsylvania State University University Park 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