@article{Bon-Cai-Duj-2006-1,
    author={Bernard Bonnard and Jean-Baptiste Caillau and Romain Dujol },
    title={Averaging and optimal control of elliptic Keplerian orbits 
           with low propulsion },
    journal={Systems Control Lett. },
    year={2006 },
    volume={55(9) },
    pages={755--760},
}