Railway Signal System, patent, May 26, 1908; (https://texashistory.unt.edu/ark:/67531/metapth509716/m1/1/: accessed June 20, 2024), University of North Texas Libraries, The Portal to Texas History, texashistory.unt.edu.; .
Railway Signal System, patent, May 26, 1908; (https://texashistory.unt.edu/ark:/67531/metapth509716/m1/1/: accessed June 20, 2024), University of North Texas Libraries, The Portal to Texas History, texashistory.unt.edu.; .