Text and Data Mining valid from 2018-10-30
Received: 3 April 2018
Accepted: 9 October 2018
First Online: 30 October 2018
Ethics approval and consent to participate
: This study was approved by the ethics committee of Daqing Oilfield General Hospital, and followed the ethical guidelines laid down in the 1975 Declaration of Helsinki.
: All participants have given consent for publication.
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