@article{DE_1976_12_12_a0,
     author = {\`E. I. Grudo},
     title = {Characteristic vectors and sets of functions of two variables and their fundamental properties},
     journal = {Differencialʹnye uravneni\^a},
     pages = {2115--2128},
     publisher = {mathdoc},
     volume = {12},
     number = {12},
     year = {1976},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1976_12_12_a0/}
}