Gull, C. D., Smith, C. L., Wooldridge, E. T., & Collins, M. (1989). A directory of sources for air and space history: Primary historical collections in United States repositories (A prelim. ed.). Washington, D.C.: National Air and Space Museum, Smithsonian Institution.

Gull, Cloyd Dake., Charles Louis Smith, E. T. Wooldridge, and Martin Collins. A Directory of Sources for Air and Space History: Primary Historical Collections in United States Repositories. A prelim. ed. Washington, D.C.: National Air and Space Museum, Smithsonian Institution, 1989.

Gull, Cloyd Dake., Charles Louis Smith, E. T. Wooldridge, and Martin Collins. A Directory of Sources for Air and Space History: Primary Historical Collections in United States Repositories. A prelim. ed. Washington, D.C.: National Air and Space Museum, Smithsonian Institution, 1989.