Institution: | a Universidad de Buenos Aires, Departamento de Computación, Pabellón I, Ciudad Universitaria, 1428 Buenos Aires, Argentina b Department of Computer Science, Catholic University of Rio de Janeiro, Rua Marquês de São Vicente, 225, Rio de Janeiro, RJ 22453-900, Brazil c University of Campinas, Institute of Computing, Caixa Postal 6176, Campinas, SP 13084-971, Brazil |