@article{Ger-Hab-Mar-2004,
    author={Joseph Gergaud and Thomas Haberkorn and Pierre Martinon },
    title={Low thrust minimum-fuel orbital transfer: an homotopic 
           approach },
    journal={Journal of Guidance, Control and Dynamics },
    year={2004 },
    month={11},
    volume={27-6 },
    pages={1046--1060},
}