@article{IM2_1971_5_6_a10,
     author = {V. A. Bolgov and A. V. Efimov},
     title = {On the rate of summability of orthogonal series},
     journal = {Izvestiya. Mathematics },
     pages = {1399--1417},
     publisher = {mathdoc},
     volume = {5},
     number = {6},
     year = {1971},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/IM2_1971_5_6_a10/}
}