@article{DAN_1966_168_6_a8,
     author = {A. I. Perov},
     title = {The zero-manifolds of solutions of multidimensional differential equations of the second order},
     journal = {Doklady Akademii Nauk},
     pages = {1254--1256},
     publisher = {mathdoc},
     volume = {168},
     number = {6},
     year = {1966},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1966_168_6_a8/}
}