1. Department of Mathematics, University of Washington, Seattle, WA 98105, USA
2. Department of Physics, State University of New York, Oneonta, NY 13825, USA
3. Department of Physics, University of Maryland, College Park, MD 20472, USA
4. Department of Physics and Astronomy, Howard University, Washington, DC 20059, USA
5. Department of Applied Mathematics and Theoretical Physics, Delaware State University, Dover, DE19901, USA
6. Natural Science Division, Pepperdine University, Malibu, CA 90263, USA
7. Mathematics Department, University of Oregon, Eugene, OR 97403-1222, USA