<cite class="book" style="font-style:normal">Dennis R. Jenkins; Tony Landis, Jay Miller (2003)      <i> American X-Vehicles: An Inventory- X-1 to X-50</i>, Monographs in Aerospace History, No. 31, NASA  <small>SP-2003-4531</small></cite>
NASA/Dennis R. Jenkins, Tony Landis, Jay Miller
<a rel="nofollow" class="external free" href="http://history.nasa.gov/monograph31.pdf">http://history.nasa.gov/monograph31.pdf</a>