1. National Cancer Institute, Bethesda, Maryland
2. Children's Hospital of Pennsylvania, Philadelphia, Pennsylvania
3. Children's National Medical Center, Washington, D.C.
4. St. Jude Children's Research Hospital, Memphis, Tennessee
5. Rainbow Babies & Children Hospital, Cleveland, Ohio
6. Johns Hopkins Hospital—Baystate, Baltimore, Maryland
7. Georgetown Hospital, Washington, D.C.
8. Texas Children's Hospital, Houston, Texas
9. Merck Research Laboratories, West Point, Pennsylvania