@article{DAN_1982_263_2_a11,
     author = {A. V. Chechkin},
     title = {Ultraoperators in the theory of information systems},
     journal = {Doklady Akademii Nauk},
     pages = {302--305},
     publisher = {mathdoc},
     volume = {263},
     number = {2},
     year = {1982},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1982_263_2_a11/}
}