@article{ZNSL_1979_82_a4,
     author = {E. V. Podsypanin},
     title = {Length of the period of a quadratic irrational},
     journal = {Zapiski Nauchnykh Seminarov POMI},
     pages = {95--99},
     publisher = {mathdoc},
     volume = {82},
     year = {1979},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZNSL_1979_82_a4/}
}