[1] Cankaya Univ, Dept Math, Ankara, Turkey
[2] Inst Space Sci, Magurele, Romania
[3] Prince Sultan Univ, Dept Math & Gen Sci, Riyadh, Saudi Arabia
[4] Birla Inst Technol & Sci Pilani, Dept Math, Hyderabad, India
[5] Univ Mhamed Bougara, Fac Sci, Dept Math, Boumerdes, Algeria
[6] Al Azhar Univ Gaza, Dept Math, Gaza, Palestine