Harhoff, Dietmar MPI for Innovation and Competition, Max Planck Society;
http://www.cepr.org/active/publications/discussion_papers/dp.php?dpno=9264 (Preprint)
Gambardella, A., Harhoff, D., & Verspagen, B. (2017). The Economic Value of Patent Portfolios. Journal of Economics & Management Strategy, 26(4), 735-756. doi:10.1111/jems.12210.