1. Optimal Trajectories for Space Navigation;Lawden,1963
2. Extremal analytical solutions for intermediate-thrust arcs in a Newtonian field;Azimov;AIAA Journal of Guidance, Control and Dynamics,2010
3. Optimality of intermediate thrust arcs of rocket trajectories;Robbins;AIAA Journal,1965
4. Supplements to the lawden's theory;Zavalishin;Applied Mathematics and Mechanics,1989
5. Necessary conditions for singular extremals based on the second variation;Kelley;AIAA Journal,1964