Affiliation: | 1. Institute of Applied Physics, C.S.I.C. C/Serrano 144, 28006 Madrid, Spain;2. Department of Applied Mathematics, Universidad de Salamanca, Avda. Fernández Ballesteros 2, 37700-Béjar, Salamanca, Spain;3. Department of Applied Mathematics, E.P.S., Universidad de Salamanca, C/Hornos Caleros 50, 05003 Ávila, Spain;4. Department of Applied Mathematics, E.P.S., Universidad de Salamanca, Avda. Requejo 33, 49022 Zamora, Spain |