1. Departamento de Matemática Aplicada, Universitat Politècnica de València, 46022 Valencia, Spain
2. Department of Mathematics, University of Kalyani, Kalyani 741235, Nadia, India
3. Department of Mathematics, Chakdaha College, Chakdaha 741222, Nadia, India
4. EINA-Departmento de Matemática Aplicada, Universidad de Zaragoza, 50018 Zaragoza, Spain