1. College of Engineering MechanicsHohai University Nanjing PR China
2. Department of MathematicsShaheed Benazir Bhutto University Khyber Pakhtunkhwa Pakistan
3. Department of MathematicsSun Yat‐sen University Guangzhou PR China
4. Department of MathematicsUniversity of Peshawar Khyber Pakhtunkhwa Pakistan