Yang, Xingge
Sheng, Guangyao
Article History
Received: 29 June 2018
Accepted: 13 November 2018
First Online: 4 December 2018
Ethics approval and consent to participate
: Written informed consent for all participants in the present study were obtain from these parents or guardians of these children before the performance of the study. The retrospective observation study was approved and reviewed by Medical ethic committee of the First Affiliated Hospital of Zhengzhou University.
: Not applicable
: The authors declare that they have no competing interests.
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