Crack, powder cocaine, and heroin : drug purchase and use patterns in six U.S. citiesRiley, Kevin JackNational Institute of Justice (U.S.)United StatesEnglishBook1998Washington, DC : U.S. Dept. of Justice, Office of Justice Programs, National Institute of Justice : Executive Office of the President, Office of National Drug Control Policy, [1998]Drug abuse—United States—StatisticsDrug dealers—United States—StatisticsCrack (Drug)—United States—StatisticsCocaine abuse—United States—StatisticsHeroin abuse—United States—StatisticsStatisticsBook