@article{DE_1974_10_2_a12,
     author = {V. V. Barkovskii},
     title = {Expansion in the eigenfunctions of two pseudodifferential operators},
     journal = {Differencialʹnye uravneni\^a},
     pages = {276--280},
     publisher = {mathdoc},
     volume = {10},
     number = {2},
     year = {1974},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1974_10_2_a12/}
}