@article{MZM_2006_80_3_a12,
     author = {V. I. Filippov},
     title = {Perturbation of the trigonometric system in~$L_1(0,\pi)$},
     journal = {Matemati\v{c}eskie zametki},
     pages = {429--436},
     publisher = {mathdoc},
     volume = {80},
     number = {3},
     year = {2006},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_2006_80_3_a12/}
}