Institution: | 1. Department of Mathematics, Georgetown University, Washington, D.C. 20057‐1233, USA;2. Phone: +1 202 687 2703, Fax: +1 202 687 6067;3. Institute of Computer Science, Acad. of Sci. of the Czech Republic, Pod Vodárenskou vě?í 2, 182 07 Prague 8, Czech Republic;4. Phone: +420 266053231, Fax: +420 286585789 |