Wang, Shaobin
Ren, Zhoupeng
Funding for this research was provided by:
National Natural Sciences Foundation of China (41502329)
Open foundation of Key Laboratory of Coal Resources Exploration and Comprehensive Utilization, Ministry of Land and Resources, P R China (KF2018-7)
Article History
Received: 13 June 2018
Revised: 6 March 2019
Accepted: 8 May 2019
First Online: 21 May 2019
Compliance with ethical standards
:
: The authors confirm that this research involved no conflict of interest.
: This article is based on a secondary analysis of administrative data and does not contain any studies with human participants performed by any of the authors.