Funding for this research was provided by:
National Natural Science Foundation of China (31470196, 31270083)
Text and Data Mining valid from 2019-03-13
Received: 6 December 2018
Revised: 17 February 2019
Accepted: 26 February 2019
First Online: 13 March 2019
Compliance with ethical standards
: The authors declare that they have no conflict of interest.
: This article does not contain any studies with human participants by any of the authors.