RT Journal Article SR Electronic T1 Electronic cigarettes, smoking and population health JF Clinical Medicine JO Clin Med FD Royal College of Physicians SP 334 OP 337 DO 10.7861/clinmedicine.14-4-334 VO 14 IS 4 A1 John Britton A1 Ilze Bogdanovica A1 Richard Ashcroft A1 Ann McNeill YR 2014 UL http://www.rcpjournals.org/content/14/4/334.abstract