Funding for this research was provided by:
National Basic Research Program of China (973 Program) (2016YFB0900101)
National Natural Science Foundation of China (51377027)
Text and Data Mining valid from 2018-01-19
Received: 16 April 2017
Accepted: 4 December 2017
First Online: 19 January 2018
: The authors declare that they have no competing interests.