@article{IM2_2008_72_1_a0,
     author = {V. I. Arnol'd},
     title = {Statistics of the periods of continued fractions for quadratic irrationals},
     journal = {Izvestiya. Mathematics},
     pages = {1--34},
     year = {2008},
     volume = {72},
     number = {1},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/IM2_2008_72_1_a0/}
}