1. School of Computer and Communication Sciences, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerlan
2. Department of Computer Science, University of Oxford, Oxford, U.K.
3. University of Amsterdam, Amsterdam, The Netherlands
4. Karlsruhe Institute of Technology, Karlsruhe, Germany
5. Department of Electrical and Computer Engineering, University of Massachusetts Amherst, Amherst, MA, USA