1. U.S. Food and Drug Administration, Center for Tobacco Products, Office of Science, Division of Product Science, 11785 Beltsville Drive, Calverton, Maryland 20705, United States
2. U.S. Food and Drug Administration, Center for Veterinary Medicine, Office of Research, Division of Residue Chemistry, 8401 Muirkirk Road, Laurel, Maryland 20708, United States
3. Centers for Disease Control and Prevention, National Center for Environmental Health, Division of Laboratory Sciences, Tobacco and Volatiles Branch, Atlanta, Georgia 30341, United States