1. a Division of Hematology and Oncology , Mayo Clinic , Jacksonville, FL, USA
2. b Nicotine Research Center , Mayo Clinic , Jacksonville, FL, USA
3. c Department of Psychiatry and Psychology , Mayo Clinic , Jacksonville, FL, USA
4. d Behavioral Health Research Program , Mayo Clinic , Jacksonville, FL, USA
5. e Division of Biostatistics , Mayo Clinic , Jacksonville, FL, USA
6. f Nicotine Dependence Center , Mayo Clinic , Jacksonville, FL, USA