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@article{DE_1981_17_1_a4, author = {N. N. Gaidai}, title = {Existence of the spectrum for the {Tricomi} operator}, journal = {Differencialʹnye uravneni\^a}, pages = {31--38}, publisher = {mathdoc}, volume = {17}, number = {1}, year = {1981}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/DE_1981_17_1_a4/} }
N. N. Gaidai. Existence of the spectrum for the Tricomi operator. Differencialʹnye uravneniâ, Tome 17 (1981) no. 1, pp. 31-38. http://geodesic.mathdoc.fr/item/DE_1981_17_1_a4/