[1] Univ Gujrat, Dept Math, Gujrat 50700, Pakistan
[2] Govt Coll Univ, Dept Math, Katchery Rd, Lahore 54000, Pakistan
[3] 1 Decembrie 1918 Univ Alba Iulia, Dept Math, Alba Iulia 510009, Romania
[4] China Med Univ, Dept Med Res, Taichung, Taiwan
[5] Univ Pretoria, Dept Math & Appl Math, Lynnwood Rd, ZA-0002 Pretoria, South Africa
[6] Tech Univ Cluj Napoca, Dept Math, Cluj Napoca 400114, Romania
[7] Princess Nourah Bint Abdulrahman Univ, Coll Sci, Dept Math Sci, POB 84428, Riyadh 11671, Saudi Arabia
[8] Mircea Cel Batran Naval Acad, Dept Math, Constanta 900218, Romania