@article{DAN_1975_221_6_a2,
     author = {M. I. Kanovitch},
     title = {A hierarchical semantic system with set variables},
     journal = {Doklady Akademii Nauk},
     pages = {1256--1259},
     publisher = {mathdoc},
     volume = {221},
     number = {6},
     year = {1975},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1975_221_6_a2/}
}