RT Journal Article SR Electronic T1 The changing landscape of crack cocaine use and HIV infection JF Canadian Medical Association Journal JO CMAJ FD Canadian Medical Association SP 571 OP 572 DO 10.1503/cmaj.091574 VO 181 IS 9 A1 Celentano, David A1 Sherman, Susan G. YR 2009 UL http://www.cmaj.ca/content/181/9/571.abstract