@article{SM_1971_15_4_a10,
     author = {L. F. Barannik and P. M. Gudivok},
     title = {Letter to the {Editor}},
     journal = {Sbornik. Mathematics},
     pages = {642},
     publisher = {mathdoc},
     volume = {15},
     number = {4},
     year = {1971},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1971_15_4_a10/}
}