title: Epidemiological field experiments to prevent heroin spread.
mesh_terms: D000488:Allied Health Personnel; D002641:Chicago; D003156:Community Mental Health Services; D004812:Epidemiologic Methods; D005500:Follow-Up Studies; D006556:Heroin Dependence / Q000453:epidemiology / Q000517:prevention & control*; D006801:Humans; D007398:Interpersonal Relations