@article{DAN_1985_283_4_a7,
     author = {A. M. Vinogradov and V. N. Gusyatnikova and V. A. Yumaguzhin},
     title = {Secondary differential operators},
     journal = {Doklady Akademii Nauk},
     pages = {801--805},
     publisher = {mathdoc},
     volume = {283},
     number = {4},
     year = {1985},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1985_283_4_a7/}
}