Affiliation: | a Department of Mathematics, University of South Carolina, Columbia, SC 29208, USA b IMATE, UNAM, Ap. Postal 61-3 (Xangari), CP. 58 089, Morelia, Michoacán, Mexico c Department of Applied Mathematics, GSEAS, Naval Postgraduate School, 833 Dyer Road, Monterey, CA 93943, USA d Department of Mathematics, Auburn University Montgomery, Montgomery, AL 36124, USA |