[Main rotor of the XH-40], photograph, November 8, 1957; (https://texashistory.unt.edu/ark:/67531/metadc950042/m1/1/: accessed July 16, 2024), University of North Texas Libraries, The Portal to Texas History, texashistory.unt.edu; .
[Main rotor of the XH-40], photograph, November 8, 1957; (https://texashistory.unt.edu/ark:/67531/metadc950042/m1/1/: accessed July 16, 2024), University of North Texas Libraries, The Portal to Texas History, texashistory.unt.edu; .