Affiliation: | 1. Department of Mathematics, Gunma National College of Technology, 580 Toriba, Maebashi, Gunma, 371-8530, Japan;2. Department of Mathematical Information Science, Tokyo University of Science, 1-3 Kagurazaka, Sinjuku-ku, Tokyo 162-8601, Japan;3. Department of Mathematical Sciences, Georgia Southern University, 65 Georgia Ave. Rm. 3008, Statesboro, GA 30460, USA |