@article{ZNSL_1985_141_a0,
     author = {A. L. Vol'berg and V. A. Tolokonnikov},
     title = {Hankel operators and problems of best approximation of unbounded functions},
     journal = {Zapiski Nauchnykh Seminarov POMI},
     pages = {5--17},
     year = {1985},
     volume = {141},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZNSL_1985_141_a0/}
}