1. Optimum Trajectories for Space Navigation;Lawden,1964
2. The problem of determining the trajectories in a Newtonian field;Azizov,1984
3. Optimality of intermediate-thrust arcs of rocket trajectories;Robbins;AIAA J.,1965
4. A supplement to Lawden's theory;Zavalishchin;Priki. Mat. Mekh.,1989
5. The use of the Levi-Civita method to analyse optimum trajectories;Azizov;Kosmich. Issledovaniya,1979