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Shuanglin ZhangRichard and Elizabeth Henes ProfessorDepartment of Mathematical Sciences Michigan Technological University 1400 Townsend Drive, 307 Fisher Hall Houghton, MI 49931-1295, U.S.A. Phone: (906) 487 2095 Fax: (906) 487 3133 E-mail: shuzhang@mtu.edu |