Funding for this research was provided by:
National Natural Science Foundation of China (81372973)
Text and Data Mining valid from 2018-08-08
Received: 1 November 2017
Accepted: 28 June 2018
First Online: 8 August 2018
Ethics approval and consent to participate
: Written informed consent was obtained from parents of the children. This study was approved by the Medical Research Ethics Committee of Wuhan University.
: Not applicable.
: The authors declare that they have no competing interests.
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