Railroad-Signal, patent, February 17, 1920; (https://texashistory.unt.edu/ark:/67531/metapth1256692/m1/1/: accessed June 26, 2024), University of North Texas Libraries, The Portal to Texas History, texashistory.unt.edu.; .
Railroad-Signal, patent, February 17, 1920; (https://texashistory.unt.edu/ark:/67531/metapth1256692/m1/1/: accessed June 26, 2024), University of North Texas Libraries, The Portal to Texas History, texashistory.unt.edu.; .