@inproceedings{Cai-Dao-Ger-2011,
    author={Jean-Baptiste Caillau and Bilel Daoud and Joseph Gergaud },
    title={Discrete and differential homotopy in circular restricted 
           three-body control },
    organization={Proceedings of 8th AIMS Conference on Dynamical Systems, 
           Differential Equations and Applications },
    booktitle={Discrete Contin. Dyn. Syst. },
    year={2011 },
    volume={Suppl. },
    pages={229--239},
}