Dr. Hasibun Naher, Lecturer in Mathematics, Department of Mathematics and Natural Sciences, BRAC University, 66 Mohakhali, Dhaka-1212, Bangladesh
E-mail: hasibun06tasauf@gmail.com

Dr. Mohamed Abd El Hamid, Professor, Department of Mathematics, Faculty of Science, Helwan University, Cairo 11785, Egypt
E-mail: seddeek_m@hotmail.com