Spring Trip-Foot, patent, February 22, 1910; (https://texashistory.unt.edu/ark:/67531/metapth512605/m1/1/: accessed July 15, 2024), University of North Texas Libraries, The Portal to Texas History, texashistory.unt.edu; .
Spring Trip-Foot, patent, February 22, 1910; (https://texashistory.unt.edu/ark:/67531/metapth512605/m1/1/: accessed July 15, 2024), University of North Texas Libraries, The Portal to Texas History, texashistory.unt.edu; .