Validity of self-reported smoking habits.
D000328:Adult; D001944:Breath Tests; D002248:Carbon Monoxide / Q000032:analysis; D003718:Denmark / Q000453:epidemiology; D006801:Humans; D008875:Middle Aged; D015203:Reproducibility of Results; D012907:Smoking / Q000453:epidemiology*; D011795:Surveys and Questionnaires / Q000592:standards*
D002248:Carbon Monoxide