@article{ZNSL_1997_237_a3,
     author = {E. P. Golubeva},
     title = {On quadratic irrationalities having continued fractions with small periods},
     journal = {Zapiski Nauchnykh Seminarov POMI},
     pages = {31--39},
     year = {1997},
     volume = {237},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZNSL_1997_237_a3/}
}