Civil Aeronautics Board report into the crash of a Mooney M-18 near Butler, PA on 7 September 1959.
Civil Aeronautics Board, US Department of Commerce
1960-06-21
US Department of Transportation, Special Collections <a rel="nofollow" class="external autonumber" href="http://specialcollection.dotlibrary.dot.gov/Contents">[1]</a>