Funding for this research was provided by:
Joint Funds of Science & Technology Department of Guizhou Province of China (LKZ[2013]02)
National Natural Science Foundation of China (81560276)
Foundation for Returnees from the Department of Human Resources and Social Security of Guizhou Province of China ([2014]08)
Article History
Received: 27 January 2018
Accepted: 2 April 2018
First Online: 6 April 2018
Compliance with ethical standard
:
: This article does not contain any studies with human participants or animals performed by any of the authors.
: On behalf of all authors, Dr. Bainan Liu states that there is no conflict of interest.