@article{DAN_1988_303_1_a3,
     author = {S. Z. Levendorskii},
     title = {Types of degenerate elliptic operators},
     journal = {Doklady Akademii Nauk},
     pages = {24--28},
     publisher = {mathdoc},
     volume = {303},
     number = {1},
     year = {1988},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1988_303_1_a3/}
}