@article{IM2_2006_70_2_a3,
     author = {A. S. Romanyuk},
     title = {Bilinear and trigonometric approximations of periodic functions},
     journal = {Izvestiya. Mathematics},
     pages = {277--306},
     year = {2006},
     volume = {70},
     number = {2},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/IM2_2006_70_2_a3/}
}