[1] Truth Initiat, Schroeder Inst Tobacco Res & Policy Studies, Washington, DC 20001 USA
[2] Georgetown Univ, Med Ctr, Dept Oncol, Canc Prevent & Control Program,Georgetown Lombard, Washington, DC 20007 USA
[3] Johns Hopkins Bloomberg Sch Publ Hlth, Dept Hlth Behav & Soc, Baltimore, MD USA
[4] WESTAT Corp, Rockville, MD 20850 USA