@article{CRMATH_2009__347_7-8_369_0,
     author = {Gudovich, Anastasia and Kamenskii, Mikhail and Quincampoix, Marc},
     title = {Existence of periodic solutions of a ordinary differential equation perturbed by a small parameter: {An} averaging approach},
     journal = {Comptes Rendus. Math\'ematique},
     pages = {369--374},
     publisher = {Elsevier},
     volume = {347},
     number = {7-8},
     year = {2009},
     doi = {10.1016/j.crma.2009.02.012},
     language = {en},
     url = {http://www.numdam.org/articles/10.1016/j.crma.2009.02.012/}
}