Affiliation: | 1. Harvard School of Engineering and Applied Sciences, Cambridge, MA 02138, USA;2. 82 Powers Road, Concord, MA 01742, USA;1. Department of Mathematics and Computer Science, Adam Mickiewicz University, Poznań 61-614, Poland;2. Institute of Mathematics, Poznań University of Technology, ul. Piotrowo 3A, 60-965 Poznań, Poland |