Institution: | (1) Department of Mathematics, University of Connecticut, U-9, MSB 111, 196, Auditorium Road, Storrs, Connecticut, 06269, U.S.A.;(2) Department of Mathematics, Joetsu University of Education, 943 Joetsu, Niigata Pref., Japan e-mail;(3) Department of Mathematics, Ichinoseki National College of Technology, 021 Ichinoseki, Iwate Pref., Japan |