1. Department of Environmental Health Sciences; University of Michigan; Ann Arbor Michigan
2. Epidemiology Unit; Prince of Songkla University; Songkhla Thailand
3. Department of Epidemiology; University of Michigan; Ann Arbor Michigan
4. Department of Pediatrics; Faculty of Medicine; Khon Kaen University; Khon Kaen Thailand
5. Department of Pediatrics; Section of Hematology-Oncology; Baylor College of Medicine; Houston Texas