@article{DAN_1980_253_6_a6,
     author = {A. A. Novruzov and I. T. Mamedov},
     title = {On $R$-identity of second-order elliptic and parabolic operators},
     journal = {Doklady Akademii Nauk},
     pages = {1314--1317},
     publisher = {mathdoc},
     volume = {253},
     number = {6},
     year = {1980},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1980_253_6_a6/}
}