@article{10_4007_annals_2005_161_141,
     author = {Nguyen Tien Zung},
     title = {Convergence versus integrability in {Birkhoff} normal form},
     journal = {Annals of mathematics},
     pages = {141--156},
     publisher = {mathdoc},
     volume = {161},
     number = {1},
     year = {2005},
     doi = {10.4007/annals.2005.161.141},
     mrnumber = {2150385},
     zbl = {1076.37045},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4007/annals.2005.161.141/}
}