1. SQIG – Instituto de Telecomunicações and IST, TU Lisbon, Portugal. E-mail: pedro.adao@ist.utl.pt
2. Department of Computer Science, UC Davis, USA. E-mail: gebana@cs.ucdavis.edu
3. The Naval Postgraduate School, Monterey, CA, USA. E-mail: jcherzog@nps.edu
4. Department of Mathematics, University of Pennsylvania, Philadelphia, PA, USA. E-mail: scedrov@math.upenn.edu