1. Oklahoma Tobacco Research Center, Oklahoma City, Oklahoma, USA;
2. Oklahoma State University, Stillwater, Stillwater, Oklahoma, USA;
3. Kent State University, Kent, Ohio, USA;
4. University of Missouri School of Medicine, Columbia, Missouri, USA;
5. University of Wisconsin - Stevens Point, Stevens Point, Wisconsin, USA;
6. Oklahoma Tobacco Research Center, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, USA