Department of Management, Economics and Quantitative Methods, Università di Bergamo, Bergamo, Italy
Department of Management, Economics and Industrial Engineering, Politecnico di Milano, Milano, Italy
Copyright © 2015 Anna Maria Falzoni, Lucia Tajoli et al. This is
an open access article distributed under the Creative Commons Attribution
License, which permits unrestricted use, distribution, and reproduction in any
medium, provided the original work is properly cited.