1. College of Energy and Mining Engineering, Shandong University of Science and Technology, Qingdao, China
2. Institute of Mathematics, Khwaja Fareed University of Engineering and Information Technology, Rahim Yar Khan, Pakistan
3. Department of Mathematics, University of Sargodha, Sargodha, Pakistan
4. School of Mines, China University of Mining and Technology, Xuzhou, Jiangsu, China