@article{DAN_1967_174_2_a11,
     author = {V. A. Yankov},
     title = {Finite validity of formulas of special form},
     journal = {Doklady Akademii Nauk},
     pages = {302--304},
     publisher = {mathdoc},
     volume = {174},
     number = {2},
     year = {1967},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1967_174_2_a11/}
}