Funding for this research was provided by:
National Natural Science Foundation of China (41671500)
Text and Data Mining valid from 2018-05-09
Received: 20 November 2017
Accepted: 27 April 2018
First Online: 9 May 2018
Ethics approval and consent to participate
: Not applicable. There was no primary data collection.
: The authors declare that they have no competing interests regarding this study.
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