De Force, Samuel A. & McConnell, William V. Improvement in Cotton Scrapers, Choppers, and Dirters., patent, December 2, 1879; (https://texashistory.unt.edu/ark:/67531/metapth169936/m1/1/: accessed July 1, 2024), University of North Texas Libraries, The Portal to Texas History, texashistory.unt.edu.; .