Mail-Transferring Apparatus., patent, April 20, 1920; (https://texashistory.unt.edu/ark:/67531/metapth1258912/m1/1/: accessed May 22, 2024), University of North Texas Libraries, The Portal to Texas History, texashistory.unt.edu; .
Mail-Transferring Apparatus., patent, April 20, 1920; (https://texashistory.unt.edu/ark:/67531/metapth1258912/m1/1/: accessed May 22, 2024), University of North Texas Libraries, The Portal to Texas History, texashistory.unt.edu; .