1. From the University of Colorado School of Medicine, Children's Hospital, Denver, Colorado;
2. University of Cincinnati College of Medicine, Children's Hospital Medical Center, Cincinnati, Ohio;
3. University of Southern California School of Medicine, Children's Hospital Los Angeles, Los Angeles, California;
4. Group Health Cooperative of Puget Sound, University of Washington School of Medicine, Seattle, Washington; and
5. University of Utah School of Medicine, Salt Lake City, Utah.