@article{ASNSP_1989_4_16_2_245_0,
     author = {Chierchia, L. and Zehnder, E.},
     title = {Asymptotic expansions of quasiperiodic solutions},
     journal = {Annali della Scuola Normale Superiore di Pisa - Classe di Scienze},
     pages = {245--258},
     publisher = {Scuola normale superiore},
     volume = {Ser. 4, 16},
     number = {2},
     year = {1989},
     mrnumber = {1041897},
     zbl = {0695.34040},
     language = {en},
     url = {http://www.numdam.org/item/ASNSP_1989_4_16_2_245_0/}
}