1. Department of Mathematics, Federal University of Paraíba, UFPB, CEP 58050-085, João Pessoa-PB, Brazil.
2. University of Sevilla, Dpto EDAN and IMUS, Aptdo 1160, 41080 Sevilla, Spain, and Department of Mathematics, Federal University of Paraíba, UFPB, CEP 58050-085, João Pessoa-PB, Brazil.
3. Inria, Sorbonne Université, Université de Paris, CNRS, Laboratoire Jacques-Louis Lions, Paris, France.
4. Federal Institute of Ceará, IFCE, CEP 62320-000, Tianguá, CE, Brazil.
5. University of Sevilla, Dpto. EDAN and IMUS, Aptdo 1160, 41080 Sevilla, Spain.