5Guerrero, D. C. , SERO, M. A. , Spatial Distribution of Pa- tents in Spain: Determining Factors and Consequences on Re-gional Development. Regional Studies, 1997, 31(4): 381- 390.
6Petruzzelli, A. M. , The Impact of Technological Related- ness, Prior Ties, and Geographical Distance on University- industry Collaborations: A joint-patent analysis. Technova- tion, 2011, 31(7): 309-319.
7Graf, H. , Henning, T, Public Research in Regional Net- works of Innovators: A Comparative Study of Four East Ger- man Regions. Regional Studies, 2009, 43(10) : 1349-1368.