Schautschick, Philipp MPI for Intellectual Property and Competition Law, Max Planck Society;
http://www.economics.ox.ac.uk/Research/wp/pdf/paper546.pdf (Preprint)
Schautschick, P., Helmers, C., & Rogers, M. (2011). Intellectual Proerty at the Firm-Level: The Oxford Intellectual Property Firm-Level Database. Oxford Working Paper Series, No. 546.