RT Journal Article SR Electronic T1 Tobacco control: comparative politics in the United States and Canada JF Tobacco Control JO Tob Control FD BMJ Publishing Group Ltd SP 436 OP 436 DO 10.1136/tc.12.4.436 VO 12 IS 4 A1 C Callard YR 2003 UL http://tobaccocontrol.bmj.com/content/12/4/436.abstract AB