@article{DE_1976_12_3_a11,
     author = {L. I. Kovalenko},
     title = {Existence of a generalized solution of the {Tricomi} {problem.~I}},
     journal = {Differencialʹnye uravneni\^a},
     pages = {511--528},
     year = {1976},
     volume = {12},
     number = {3},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1976_12_3_a11/}
}