[1] Sri Vijay Vidyalaya Coll Arts & Sci, Dept Math, Dharmapuri 636807, India
[2] Alagappa Univ, Ramanujan Ctr Higher Math, Karaikkudi 630004, Tamil Nadu, India
[3] Nanjing Normal Univ, Sch Math Sci, Nanjing 210023, Jiangsu, Peoples R China
[4] Nanjing Normal Univ, Inst Finance & Stat, Nanjing 210023, Jiangsu, Peoples R China
[5] Univ Bielefeld, Dept Math, D-33615 Bielefeld, Germany
[6] Khadir Mohideen Coll, Dept Math, Adirampattinam 614701, Thanjavur, India
[7] Nanjing Xiaozhuang Univ, Sch Math & Informat Technol, Nanjing 211171, Jiangsu, Peoples R China