The Armstrong Whitworth A.W. XVI military Airplane (British) : a single-seat biplane (1932)
NASA Technical Reports Server (NTRS) · leaf 10
N.A.C.A. Aircraft Circular Ho. 156 Fl««. 17.18,19.20,21 Pigs. 18,19,20 Ixamples of steel tube construction, showing in particular, the hall and cup method of attaching the vertical fuselage struts.
NASA Technical Reports Server (NTRS)
Internet Archive · NASA Technical Reports · Public domain (US government work). Free to use for anything.
