@article{ZNSL_2011_389_a1,
     author = {S. V. Bykov},
     title = {Extension of a~theorem by {Hardy} and {Littlewood}},
     journal = {Zapiski Nauchnykh Seminarov POMI},
     pages = {21--33},
     publisher = {mathdoc},
     volume = {389},
     year = {2011},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZNSL_2011_389_a1/}
}