Omenn 1988.

Methods	Setting: single worksite (13,000 workers, 9 employers), USA Recruitment: worksite volunteers
Participants	243 smokers with preference for a self‐help programme
Interventions	Only self‐help format conditions considered in this review ∙ Multiple‐component programme ∙ Relapse prevention programme ∙ Minimal treatment programme (American Cancer Society Quitter's Guide; 7‐day plan)
Outcomes	Abstinence at 12 months Validation: saliva cotinine ≤ 35 ng/mL
Notes	Comparison between self‐help materials; not in meta‐analysis No clinical or statistically significant differences between quit rates in the 3 groups
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "nurses at aid stations using randomized assignment lists generated by research centre, within preference for format"
Allocation concealment (selection bias)	Unclear risk	No details given
Blinding (performance bias and detection bias) All outcomes	Low risk	Biochemical validation; interventions of similar intensities
Incomplete outcome data (attrition bias) All outcomes	Low risk	At least 89% followed up in each arm; non‐respondents counted as smokers