@article{MZM_1988_44_1_a13,
     author = {N. G. Khor'kova},
     title = {Conservation laws and nonlocal symmetries},
     journal = {Matemati\v{c}eskie zametki},
     pages = {134--144},
     publisher = {mathdoc},
     volume = {44},
     number = {1},
     year = {1988},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1988_44_1_a13/}
}