1. Department of Mathematics & Physics, North Carolina Central University, Durham, NC 27707, USA
2. Área de Electromagnetismo and Grupo Interdisciplinar de Sistemas Complejos (GISC), Universidad Rey Juan Carlos, 28933 Móstoles, Madrid, Spain
3. Laboratoire Charles Coulomb (L2C), UMR 5221 CNRS-University of Montpellier, F-34095 Montpellier, France
4. Department of Physics, University of South Florida, Tampa, FL 33620, USA
5. Institut Universitaire de France, 1 rue Descartes, F-75231 Paris Cedex 05, France