Keutzer 1968.

Methods	Randomized 'with consideration of evenings convenient for subjects' Therapists: All treatments run by same 2 therapists Treatment: 5 sessions over 5w, 4 in groups (group size not stated)
Participants	Cigs/day: 28. Age: 40
Interventions	1. 'Coverant control' ‐ 'high probability behaviour made contingent on anti‐smoking thoughts' 2. Image of smoking paired with holding breath for 10‐20 secs ('aversive consequence') 3. Puff every 12 secs on 3 cigarettes in a smoky room 4. Placebo 'drug' 5. Untreated controls
Outcomes	Follow up contacts: 6m by posted questionnaire (reported in Lichtenstein 1969) Outcome: Abstinence at 6m Validation: None
Notes	Inclusions: 3 vs 4 in Other Methods analysis, 3 vs 2 in Dose‐Response analysis Notes: No data on continuous abstinence, not validated