Department of Economics and Management, North China Electric Power University,
689 Huadian Road, Baoding 071000, China
Submission date: 2017-04-04
Acceptance date: 2017-05-08
Online publication date: 2017-10-02
Publication date: 2017-11-07
Pol. J. Environ. Stud. 2017;26(6):2851–2860