@article{DAN_1973_208_6_a2,
     author = {G. G. Kazaryan},
     title = {Comparison of differential operators, and differential operators of constant strength},
     journal = {Doklady Akademii Nauk},
     pages = {1272--1275},
     publisher = {mathdoc},
     volume = {208},
     number = {6},
     year = {1973},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1973_208_6_a2/}
}