
Shuanglin ZhangRichard and Elizabeth Henes ProfessorDepartment of Mathematical Sciences Michigan Technological University 1400 Townsend Drive, 307 Fisher Hall Houghton, MI 499311295, U.S.A. Phone: (906) 487 2095 Fax: (906) 487 3133 Email: shuzhang@mtu.edu 