Text and Data Mining valid from 2018-08-29
Received: 6 June 2018
Accepted: 20 August 2018
First Online: 29 August 2018
Ethics approval and consent to participate
: This study was conducted under compliance with the Declaration of Helsinki and were approved by sixth people’s hospital of Qingdao.
: Not applicable.
: The authors declare that they have no competing interests.
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