@article{DE_1984_20_12_a2,
     author = {V. I. Gromak},
     title = {Nonlinear evolution equations and equations of $P$-type},
     journal = {Differencialʹnye uravneni\^a},
     pages = {2042--2048},
     publisher = {mathdoc},
     volume = {20},
     number = {12},
     year = {1984},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1984_20_12_a2/}
}