Institution: | 1. Department of Mathematics, CMUC, University of Coimbra, Coimbra, Portugal.bebiano@mat.uc.pt;3. Department of Physics, University of Coimbra, Coimbra, Portugal.;4. Department of Mathematics, CMUC, Polytechnic Institute of Tomar, Tomar, Portugal.;5. Department of Physics, University of Beira Interior, Covilh?, Portugal. |