Funding for this research was provided by:
program of Guizhou Provincial Science and Technology Department (7415)
Text and Data Mining valid from 2019-02-08
Received: 16 August 2018
Accepted: 28 January 2019
First Online: 8 February 2019
Compliance with ethical standards
: The authors have declared that no conflict of interest exists.
: This article does not contain any studies with human participants or animals performed by any of the authors.