- Correspondence to Professor Eun-Cheol Park, Department of Preventive Medicine, College of Medicine, and Institute of Health Services Research, Yonsei University, 50-1 Yonsei-ro, Seodaemun-gu, Seoul 120-752, Republic of Korea;
- Received January 18, 2016
- Revision received June 17, 2016
- Accepted August 7, 2016
- First published September 22, 2016.
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