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3. C. Marshal, J.-P. Marec, C.B. Winn, Synthesis of the analytical results on optimal transfers between Keplerian orbits, Proceedings of the XVIII Astronautic International Congress, Belgrade, 25–29 September 1967, T.P.515 (1967), p. 35 (in French).
4. Chemical and solar electric propulsion options for a cornerstone mission to Mercury;Langevin;Acta Astronautica,2000
5. Asymptotic optimization of very long, low thrust propelled inter-orbital maneuvers;Guelman;Acta Astronautica,2000