1. Department of Preventive Medicine, Korea University College of Medicine, Seoul, Korea.
2. Department of Pediatrics, Korea University Anam Hospital, Seoul, Korea.
3. Department of Pediatrics, Incheon Sejong Hospital, Incheon, Korea.
4. Department of Pediatrics, Chungbuk National University Hospital, Cheongju, Korea.
5. Department of Pediatrics, Seoul Metropolitan Government - Seoul National University Boramae Medical Center, Seoul, Korea.
6. Department of Pediatrics, Seoul National University Hospital, Seoul, Korea.