[1] UNIV N CAROLINA, SCH MED, LINEBERGER COMPREHENS CANC CTR, CHAPEL HILL, NC 27514 USA
[2] UNIV N CAROLINA, SCH PUBL HLTH, DEPT BIOSTAT, CHAPEL HILL, NC 27514 USA
[3] RES TRIANGLE INST, RES TRIANGLE PK, NC 27709 USA
[4] BURROUGHS WELLCOME CO, RES TRIANGLE PK, NC 27709 USA
[5] UNIV MASSACHUSETTS, SCH MED, DEPT PEDIAT, WORCESTER, MA 01605 USA
[6] MASSACHUSETTS GEN HOSP, DEPT MED, BOSTON, MA 02114 USA
[7] MICHIGAN STATE UNIV, SCH MED, DEPT MED, E LANSING, MI 48824 USA
[8] CHILDRENS HOSP, PHILADELPHIA, PA 19104 USA
[9] ST JUDE CHILDRENS RES HOSP, MEMPHIS, TN 38101 USA
[10] UNIV TEXAS, SCH MED, DEPT PEDIAT, SAN ANTONIO, TX 78285 USA
[11] HOP ST JUSTINE, DEPT MICROBIOL & IMMUNOL, MONTREAL H3T 1C5, QUEBEC, CANADA
[12] UNIV MONTREAL, MONTREAL H3C 3J7, QUEBEC, CANADA