Frederick William Lanchester, Aerodonetics: Constituting the second volume of a complete work on aerial flight, (London, England: Archibald Constant Co. Ltd., 1908), p. viii and p. 348.
'Investigation of the Helios Prototype Aircraft Mishap Volume I Mishap Report', Thomas E. Noll, NASA Langley Research Center, 2004, http://www.nasa.gov/pdf/64317main_helios.pdf
