Clay, Henry, Jr. [Letter from Henry Clay, Jr. to his Mother and Family, September 22, 1917], letter, September 22, 1917; (https://texashistory.unt.edu/ark:/67531/metapth706152/m1/1/: accessed December 12, 2018), University of North Texas Libraries, The Portal to Texas History, texashistory.unt.edu; .