1. Department of Computer Science, University of Illinois at Urbana-Champaign, Urbana, IL, USA
2. Department of Computer Science, Centro de Investigacion en Matematicas (CIMAT), Guanajuato, Mexico
3. Consejo Nacional de Ciencia y Tecnologia (CONACYT), Mexico City, Mexico
4. Faculty of Information Technology and Electrical Engineering, University of Oulu, Oulu, Finland