Funding for this research was provided by:
National Research Foundation of Korea (2010-0026225)
Text and Data Mining valid from 2018-07-27
Received: 25 April 2018
Accepted: 20 July 2018
First Online: 27 July 2018
Ethics approval and consent to participate
: The study protocol was approved by ethics committee of the Ewha Womans University Mokdong Hospital Institutional Review Board, and written consent was obtained from the parents of each subject.
: Not applicable
: The authors declare that they have no competing interests.
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