@article{ASNSP_1998_4_26_4_623_0,
     author = {Kappeler, Thomas and Kodama, Yuji and N\'emethi, Andras},
     title = {On the {Birkhoff} normal form of a completely integrable hamiltonian system near a fixed point with resonance},
     journal = {Annali della Scuola Normale Superiore di Pisa - Classe di Scienze},
     pages = {623--661},
     publisher = {Scuola normale superiore},
     volume = {Ser. 4, 26},
     number = {4},
     year = {1998},
     mrnumber = {1648558},
     zbl = {0919.58030},
     language = {en},
     url = {http://archive.numdam.org/item/ASNSP_1998_4_26_4_623_0/}
}