1. Center for Tobacco Research and Intervention, University of Wisconsin School of Medicine and Public Health, Madison, WI, USA
2. University of Wisconsin School of Medicine and Public Health, Department of Medicine, Madison, WI, USA
3. William S. Middleton Memorial Veterans Hospital, Madison, WI, USA
4. The Methodology Center, The Pennsylvania State University, University Park, PA, USA
5. Department of Human Development and Family Studies, The Pennsylvania State University, University Park, PA, USA
6. Institute for Health Research and Policy, University of Illinois at Chicago, Chicago, IL, USA