1. Department of General Education, Anhui Xinhua University, Hefei 230088, China
2. Department of Mathematics, COMSATS University Islamabad, Lahore Campus, Lahore, Pakistan
3. Department of Mathematics, COMSATS University Islamabad, Vehari Campus, Vehari 61100, Pakistan
4. Department of Mathematics and Statistics, Institute of Southern Punjab, Multan, Pakistan
5. School of Mathematics and Physics, Anhui Jianzhu University, Hefei, China