@article{IM2_1987_28_1_a5,
     author = {A. I. Stepanets},
     title = {Classification of periodic functions and the rate of convergence of their {Fourier} series},
     journal = {Izvestiya. Mathematics },
     pages = {99--132},
     publisher = {mathdoc},
     volume = {28},
     number = {1},
     year = {1987},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/IM2_1987_28_1_a5/}
}