1. Centro
ALGORITMI, Department of Informatics, University of Minho, 4710-057, Braga, Portugal
2. Applied
Mathematics and Computer Science, Ghent University, Krijgslaan
281 S9, 9000 Ghent, Belgium
3. Dipartimento
di Chimica “G. Ciamician”, Università di Bologna, V. F. Selmi 2, 40126 Bologna, Italy