1. University of Pisa,Via G. Caruso 16,Dept. of Information Engineering,Pisa,Italy,56122
2. Politecnico di Milano,Dept. of Electronic, Information and Bioengineering, Via G. Ponzio, 34,Milan,Italy,20133
3. CNIT - University of Pisa,Dept. of Information Engineering, Via G. Caruso 16,Pisa,Italy,56122