1. Department of Computer Science, Centre for Discrete Mathematics and its Applications (DIMAP); University of Warwick; Coventry United Kingdom
2. Department of Computer Science; Weizmann Institute of Science; Rehovot Israel
3. School of Electrical Engineering, Tel Aviv University; Tel Aviv 69978 Israel
4. Sandia National Laboratories; Livermore California
5. School of Mathematics, Tel-Aviv University, Tel-Aviv, Israel, and Schools of Mathematics and Computer Science, Georgia Institute of Technology; Atlanta GA 30332 USA
6. Department of Computer Science; TU Dortmund University; Dortmund Germany