Funding for this research was provided by:
National Natural Science Foundation of China (8167120816)
Text and Data Mining valid from 2018-04-17
Received: 19 October 2017
Accepted: 10 April 2018
First Online: 17 April 2018
Ethics approval and consent to participate
: Not applicable.
: The authors declare that they have no competing interests.
: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.