1. Balboa’s expedition is described in Samuel E. Morison, The European Discovery of America: The Southern Voyages (New York: Oxford University Press, 1974), pp. 200–204.
2. Harry L. Shipman, Space 2000: Meeting the Challenge of a New Era (New York: Plenum, 1987).
3. For instance, see Sally K. Ride, Leadership and America’s Future in Space (Washington, D.C.: NASA, 1987).
4. James Oberg and Alcestis Oberg, Pioneering Space: Living on the Next Frontier (New York: McGraw-Hill, 1986).
5. National Commission on Space, Pioneering the Space Frontier (New York: Bantam, 1986).