1. Italian National Research Council, 00185 Rome, Italy and Birkbeck, University of London, London WC1E 7HX, UK
2. Italian National Research Council, 00185 Rome, Italy, London School of Economics and Centre for Innovation Management Research, Birkbeck, University of London, London, UK
3. Birkbeck, University of London, Malet Street, London WC1E 7HX, UK