Tham khảo Boeing_Model_6

  1. Bowers, 1989, pg. 48
  2. Bowers, 1989, pg. 51
  • Bowers, Peter M. Boeing aircraft since 1916. London: Putnam Aeronautical Books, 1989. ISBN 0-85177-804-6.
  • Taylor, Michael J. H. (1989). Jane's Encyclopedia of Aviation. London: Studio Editions. tr. 170. 
  • World Aircraft Information Files. London: Bright Star Publishing. tr. File 890 Sheet 50.