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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 June 26, 2022), University of North Texas Libraries, The Portal to Texas History, texashistory.unt.edu; .