- Correspondence to Professor Sung-il Cho, Seoul National University Graduate School of Public Health, #1 Gwanak-ro, Gwanak-gu, Seoul 151-742, Republic of Korea;
- Received January 12, 2015
- Revised May 26, 2015
- Accepted May 27, 2015
- First published June 22, 2015.
If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.