Tham khảo Bell_H-12

Chú thích
  1. 1 2 3 Pelletier 1992, p. 92.
  2. ↑ Pelletier 1992, p. 91.
Tài liệu
  • Andrade, John M. U.S.Military Aircraft Designation and Serials since 1909. Leicester, UK: Midland Counties Publications, 1979. ISBN 0-904597-22-9.
  • The Illustrated Encyclopedia of Aircraft (Part Work 1982-1985). London, Orbis Publishing, 1985.
  • Pelletier, A.J. Bell Aircraft since 1935. London: Putnam & Company Ltd., 1992. ISBN 1-55750-056-8.