Under-Drilling Bit., patent, July 15, 1913; (https://texashistory.unt.edu/ark:/67531/metapth854000/m1/1/: accessed June 26, 2024), University of North Texas Libraries, The Portal to Texas History, texashistory.unt.edu.; .
Under-Drilling Bit., patent, July 15, 1913; (https://texashistory.unt.edu/ark:/67531/metapth854000/m1/1/: accessed June 26, 2024), University of North Texas Libraries, The Portal to Texas History, texashistory.unt.edu.; .