Institution: | a Università di Roma “La Sapienza”, Department of Computer Science, Via Salaria 113, 00198 Roma, Italy b ROSAEC center, Seoul National University, 599 Gwanak-ro Gwanak-gu, 151-742 Seoul, Republic of Korea c University of Ghent, Department of Pure Mathematics and Computer Algebra, Krijgslaan 281, B9000 Gent, Belgium |