Institution: | 1. Department of Computer and Information Science, University of Pennsylvania, Philadelphia, PA 19104, USA;2. Department of Computer Science, Bryn Mawr College, Bryn Mawr, PA 19010, USA;3. Departmento de Informática e Matemática Aplicada, Universidade Federal do Rio Grande do Norte, Natal (RN) CEP: 59078-870, Brazil |