Text and Data Mining valid from 2018-09-10
Received: 3 March 2018
Accepted: 12 July 2018
First Online: 10 September 2018
Ethics approval and consent to participate
: The study design was approved by the Ethical Committee of Hiroshima University (No. 1814) and informed consent was obtained from all participants and individuals in parental authority.
: Not applicable.
: The authors declare that they have no competing interests.
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