Funding for this research was provided by:
National Natural Science Foundation of China (71472184)
Text and Data Mining valid from 2018-08-06
Received: 22 June 2017
Accepted: 6 July 2018
First Online: 6 August 2018
: The authors declare that they have no competing interest.
: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.