Boeing UTTAS prototype
U.S. Department of Defense
1972
<a rel="nofollow" class="external text" href="https://babel.hathitrust.org/cgi/imgsrv/download/pdf?id=uiug.30112106757336;orient=0;size=100;seq=101;attachment=0">Military Review</a>, November 1972, Vol. 55, No. 8, Page 99.