1. The effectiveness of methadone maintenance treatment: Patients, programs, services, and outcome;Ball,1991
2. The moderator–mediator variable distinction in social psychological research: Conceptual, strategic, and statistical considerations;Baron;Journal of Personality and Social Psychology,1986
3. Centers for Disease Control. Online at: http://www.cdc.gov/hiv/topics/testing/resources/slidesets/pdf/testing_healthcare.pdf./url>. [Accessed July 5, 2007].
4. The reliability and validity of a scale to measure HIV risk-taking behaviour among intravenous drug users;Darke;AIDS,1991
5. The impact of providing incentives for attendance at AIDS prevention sessions;Deren;Public Health Reports,1994