(1) Department of Mathematics, Royal Institute of Technology, S-100 44 Stockholm, Sweden;(2) U.C.L.A., 90024 Los Angeles, CA, USA;(3) Department of Mathematics, California Institute of Technology, 91125 Pasadena, CA, USA
Abstract:
This material is based upon work supported by the National Science Foundation under grant No. DMS-9207071. The US Government
has certain rights in this material.