8Bessen J. , 2008, The Value of US patents by Owner and Patent Characteristics [J]. Research Policy, 37 (5), 932-945.
9Borregaard S , Rydfjord A. , A Study of Patent Portfolio Benchmark Methodologies & An Analy- sis of the Situation in the Telecom Industry [D ]. Master Thesis of Chalmers University of Technology, 2012.
10Brockhoff K. K. , 1991, Indicators of Firm Patent Activities [R]. Technology Management: the New International Language, IEEE, 476-481.