Funding for this research was provided by:
National Natural Science Foundation of China (31622002, 41506163, 3160010182)
Text and Data Mining valid from 2018-06-08
Received: 30 January 2018
Accepted: 25 May 2018
First Online: 8 June 2018
Ethics approval and consent to participate
: Not applicable.
: The authors declare that they have no competing interests.
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