Affiliation: | (1) Institute of Mathematics, University of Trondheim, N-7034 Trondheim, NTH, Norway;(2) Mathematics Institute, University of Copenhagen, DK-2100 Copenhagen Ø, Denmark;(3) Department of Mathematics, University of Toronto, M5S 1A1 Toronto, Ontario, Canada;(4) Department of Mathematics, University College of Swansea, SA2 8PP Swansea, Wales, U.K.;(5) Department of Mathematics, College of General Education, Tôhoku University, Sendai, Japan;(6) Present address: Mathematics Institute, University of Oslo, P.B. 1053-Blindern, N-0316 Oslo 3, Norway;(7) Present address: Department of Mathematics, Hokkaido University, 060 Sapporo, Japan |