Polydrug use and implications for longitudinal research: ten-year trajectories for heroin, cocaine, and methamphetamine users.
Brecht ML, Huang D, Evans E, Hser YI. Polydrug use and implications for longitudinal research: ten-year trajectories for heroin, cocaine, and methamphetamine users. Drug Alcohol Depend. 2008 Aug 01; 96(3):193-201.