@article{DAN_1980_251_3_a8,
     author = {G. A. Mirzoev},
     title = {Quasiregular differential operators of fourth order},
     journal = {Doklady Akademii Nauk},
     pages = {550--553},
     year = {1980},
     volume = {251},
     number = {3},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1980_251_3_a8/}
}