@article{DAN_1980_253_6_a0,
     author = {A. M. Vinogradov and I. S. Krasil'shchik},
     title = {A method of computing higher symmetries of nonlinear evolution equations, and nonlocal symmetries},
     journal = {Doklady Akademii Nauk},
     pages = {1289--1293},
     publisher = {mathdoc},
     volume = {253},
     number = {6},
     year = {1980},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1980_253_6_a0/}
}