Funding for this research was provided by:
Korea Centers for Disease Control & Prevention (2016-E33004-00)
Text and Data Mining valid from 2018-03-13
Received: 12 December 2017
Accepted: 2 March 2018
First Online: 13 March 2018
Ethics approval and consent to participate
: Not applicable. This study was conducted using secondary data.
: Not applicable.
: The authors declare that they have no competing interests.
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