Automatic Telephone-Exchange System., patent, December 5, 1893; (https://texashistory.unt.edu/ark:/67531/metapth173583/m1/1/: accessed May 25, 2024), University of North Texas Libraries, The Portal to Texas History, texashistory.unt.edu; .
Automatic Telephone-Exchange System., patent, December 5, 1893; (https://texashistory.unt.edu/ark:/67531/metapth173583/m1/1/: accessed May 25, 2024), University of North Texas Libraries, The Portal to Texas History, texashistory.unt.edu; .