Funding for this research was provided by:
National Natural Science Foundation of China (31370152, 31570099)
Text and Data Mining valid from 2019-01-31
Received: 6 August 2018
Accepted: 14 December 2018
First Online: 31 January 2019
Compliance with ethical standards
: The authors declare that they have no competing interests.
: This article does not contain any studies with human participants or animals performed by any of the authors.