@article{AIHPA_1998__68_4_507_0,
     author = {Zhang, Xu-Sheng and Vivaldi, Franco},
     title = {Small perturbations of a discrete twist map},
     journal = {Annales de l'I.H.P. Physique th\'eorique},
     pages = {507--523},
     publisher = {Gauthier-Villars},
     volume = {68},
     number = {4},
     year = {1998},
     mrnumber = {1634314},
     zbl = {0932.37025},
     language = {en},
     url = {http://www.numdam.org/item/AIHPA_1998__68_4_507_0/}
}