Funding for this research was provided by:
National Natural Science Fundation of China (81672591)
Text and Data Mining valid from 2018-08-29
Received: 16 May 2018
Accepted: 15 August 2018
First Online: 29 August 2018
Ethics approval and consent to participate
: Not applicable.
: All authors agree to the submission of this article for publication.
: The authors declare that they have no competing interests.
: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.