Institution: | (1) IBM Department of Mathematical Sciences, T.J. Watson Research Center, P.O. Box 218, Yorktown Heights, NY 10598, USA (e-mail: cam@watson.ibm.com) , US;(2) Institute of Mathematics, University of Erlangen-Nuremberg, Bismarckstr. 1 1/2, D-91054 Erlangen, Germany (e-mail: sauer@mi.uni-erlangen.de) , DE |