@article{DAN_1984_275_5_a3,
     author = {A. M. Vinogradov and I. S. Krasil'shchik},
     title = {On the theory of nonlocal symmetries of nonlinear partial},
     journal = {Doklady Akademii Nauk},
     pages = {1044--1049},
     year = {1984},
     volume = {275},
     number = {5},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1984_275_5_a3/}
}