Patents, Engineering Professionals, and the Pipelines of Innovation: The Internalization of Technical Discovery by Nineteenth-Century American Railroads

Steven Usselman, Learning by Doing in Markets, Firms, and Countries (University of Chicago Press, 1999), chap. 2, https://www.nber.org/books-and-chapters/learning-doing-markets-firms-and-countries/patents-engineering-professionals-and-pipelines-innovation-internalization-technical-discovery.