Funding for this research was provided by:
National Natural Science Foundation of China (11561023, 11461025)
Natural Science Foundation of Gansu Province (1606RJZA003)
Research Project Funds for Higher Education Institutions of Gansu Province (2016B-005)
Fundamental Research Funds for the Central Universities of Northwest MinZu University (31920180116, 31920170010)
Text and Data Mining valid from 2019-02-21
First Online: 21 February 2019
Compliance with ethical standards
: The author declares that there is no conflict of interests.
: This article does not contain any studies with human participants or animals performed by any of the authors.