1. "The Inexpensive Attainment of High Altitudes with Balloon Launched Rockets," by J. A. Van Allen and M. B. Gottlieb, published in the book, "Rocket Exploration of the Upper Atmosphere"; Pergamon Press, London,1954, and Interscience Publishers, New York, 1954, pp.53-64.
2. Private communication, J. A. Van Allen, April 1954.
3. "Rocket Propulsion Elements," byG. P. Sutton, John Wiley and Sons, New York, 1949, pp.58and 59.