@article{DE_1975_11_4_a12,
     author = {V. P. Egorov},
     title = {The extremum principle for the generalized {Neumann--Tricomi} problem},
     journal = {Differencialʹnye uravneni\^a},
     pages = {708--712},
     publisher = {mathdoc},
     volume = {11},
     number = {4},
     year = {1975},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1975_11_4_a12/}
}