Smithers, W. D. (Wilfred Dudley), 1895-1981. The border air patrol 1918-1919. Picture, artwork, 1920; (https://texashistory.unt.edu/ark:/67531/metapth11931/m1/1/: accessed March 30, 2020), University of North Texas Libraries, The Portal to Texas History, texashistory.unt.edu; .