@article{DE_1973_9_1_a13,
     author = {A. M. Nakhushev},
     title = {The correct formulation of boundary value problems for parabolic equations with a characteristic form of variable sign},
     journal = {Differencialʹnye uravneni\^a},
     pages = {130--135},
     publisher = {mathdoc},
     volume = {9},
     number = {1},
     year = {1973},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1973_9_1_a13/}
}