De Havilland DH.83 photo from NACA-AC-162
NACA Aircraft Circular
1932-05-01
<a rel="nofollow" class="external free" href="https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930090463.pdf">https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930090463.pdf</a>