Funding for this research was provided by:
qian-xue chen (81572489)
Text and Data Mining valid from 2018-11-01
Received: 6 March 2018
Accepted: 25 September 2018
First Online: 1 November 2018
Ethics approval and consent to participate
: Ethical approval was waived since we used only publicly available data and materials in this study.
: Not applicable.
: The authors declare that they have no competing interests.
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