- 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 27 December 2015
- Revision received 28 February 2016
- Accepted 5 March 2016
- Published in print 1 April 2017.
- Published online 28 March 2017.
- Published first 15 April 2016.
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