Hamilton, William L. & McCullough, George.Valve-Closure for Ventilators,
patent,
December 20, 1917;
[Washington D.C.].
(https://texashistory.unt.edu/ark:/67531/metapth1256802/m1/1/:
accessed June 26, 2024),
University of North Texas Libraries, The Portal to Texas History, https://texashistory.unt.edu;
crediting UNT Libraries Government Documents Department.