@article{DAN_1991_319_1_a10,
     author = {A. I. Omarov},
     title = {A syntactical description of filtering formulas},
     journal = {Doklady Akademii Nauk},
     pages = {58--60},
     publisher = {mathdoc},
     volume = {319},
     number = {1},
     year = {1991},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1991_319_1_a10/}
}