Sell, Friedrich L. “On the Trail of the Intangible: A Theoretical and Empirical Investigation of Innovations and Patents in Germany in the Years 2006-2019”. International Entrepreneurship Review 8, no. 1 (March 31, 2022): 47–64. Accessed April 29, 2024. https://ier.uek.krakow.pl/pm/article/view/2064.