@article{ZNSL_1991_196_a0,
     author = {E. P. Golubeva},
     title = {Quadratic irrationals with the fixed length of the period of the expansion in the continued fraction},
     journal = {Zapiski Nauchnykh Seminarov POMI},
     pages = {5--30},
     year = {1991},
     volume = {196},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZNSL_1991_196_a0/}
}