1. Department of Mathematics, State University of Maringá, Maringá, PR, Brazil;
2. Federal Technological University of Paraná, Campus Campo Mourão, Campo Mourão, PR, Brazil;
3. Department of Mathematics, Izmir Institute of Technology, Izmir, Turkey;
4. Centro de Investigación en Ingeniería Matemática & Departamento de Ingeniería Matemática, Universidad de Concepción, Concepción, Chile