Funding for this research was provided by:
Science Fund for Creative Research Groups (61421002)
National Natural Science Foundation of China (61471085, 61771112, 61671115)
Text and Data Mining valid from 2019-02-28
Received: 4 December 2018
Accepted: 18 February 2019
First Online: 28 February 2019
: Not applicable.
: The authors declare that they have no competing interests.
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