Improvement in Double-Bitted Drills., patent, May 30, 1876; (https://texashistory.unt.edu/ark:/67531/metapth166554/m1/1/: accessed June 22, 2024), University of North Texas Libraries, The Portal to Texas History, texashistory.unt.edu.; .
Improvement in Double-Bitted Drills., patent, May 30, 1876; (https://texashistory.unt.edu/ark:/67531/metapth166554/m1/1/: accessed June 22, 2024), University of North Texas Libraries, The Portal to Texas History, texashistory.unt.edu.; .