@article{ZNSL_1987_160_a6,
     author = {E. P. Golubeva},
     title = {On the period length of the continued fraction expansion of a quadratic irrational and the class number of real quadratic fields},
     journal = {Zapiski Nauchnykh Seminarov POMI},
     pages = {72--81},
     publisher = {mathdoc},
     volume = {160},
     year = {1987},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZNSL_1987_160_a6/}
}