1. Department of Family Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
2. Department of Family Medicine, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Korea.
3. Department of Family Medicine, Inje University Busan Paik Hospital, Inje University College of Medicine, Busan, Korea.
4. Department of Family Medicine, Vievisnamuh Hospital, Seoul, Korea.
5. Department of Family Medicine, Yonsei University College of Medicine, Seoul, Korea.
6. Department of Family Medicine, Pusan National University Yangsan Hospital, Pusan National University School of Medicine, Yangsan, Korea.