1. Wege zur Raumschiffahrt;OBERTH,1929
2. Minimal Trajectories;LAWDEN;J. Bis.,1950
3. Minimal Rocket Trajectories;LAWDEN;Jet Propulsion,1953
4. Fundamentals of Space Navigation;LAWDEN;J. Bis.,1954
5. The Optimization of Trajectories;BREAKWELL;SIAM Journal,1959