Hammer, patent, February 21, 1911; (https://texashistory.unt.edu/ark:/67531/metapth508704/m1/1/: accessed July 6, 2024), University of North Texas Libraries, The Portal to Texas History, texashistory.unt.edu.; .
Hammer, patent, February 21, 1911; (https://texashistory.unt.edu/ark:/67531/metapth508704/m1/1/: accessed July 6, 2024), University of North Texas Libraries, The Portal to Texas History, texashistory.unt.edu.; .