[1] Zhejiang Normal Univ, Dept Math, Jinhua 321004, Zhejiang, Peoples R China
[2] King Faisal Univ, Dept Basic Sci, Al Hufuf 31982, Al Hasa, Saudi Arabia
[3] Princess Nourah Bint Abdulrahman Univ, Dept Math Sci, Coll Sci, POB 84428, Riyadh 11671, Saudi Arabia
[4] Pontificia Univ Catolica Ecuador, Fac Ciencias Nat & Exactas, Escuela Ciencias Fis & Matemat, Sede Quito 17012184, Ecuador