@article{AIF_1995__45_3_859_0,
     author = {Gramchev, Todor and Popov, Georgi},
     title = {Nekhoroshev type estimates for billiard ball maps},
     journal = {Annales de l'Institut Fourier},
     pages = {859--895},
     publisher = {Association des Annales de l{\textquoteright}institut Fourier},
     volume = {45},
     number = {3},
     year = {1995},
     doi = {10.5802/aif.1477},
     mrnumber = {97a:58145},
     language = {en},
     url = {http://archive.numdam.org/articles/10.5802/aif.1477/}
}