1. ESTGA - Águeda School of Technology and Management, University of Aveiro, Águeda, Portugal
2. CIDMA - Center for Research & Development in Mathematics and Applications, University of Aveiro, Aveiro, Portugal
3. DMat - Mathematics Department, University of Aveiro, Aveiro, Portugal
4. Departamento de Matemática and CEMAT, IST Universidade de Lisboa, Lisboa, Portugal