@article{DE_1984_20_4_a10,
     author = {L. I. Kamynin and B. N. Khimchenko},
     title = {Theorems on the sign of a derivative for a second-order elliptic-parabolic equation},
     journal = {Differencialʹnye uravneni\^a},
     pages = {641--652},
     publisher = {mathdoc},
     volume = {20},
     number = {4},
     year = {1984},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1984_20_4_a10/}
}