@article{DAN_1977_234_2_a1,
     author = {V. A. Vershinin},
     title = {On certain operations over constructive sets with equality},
     journal = {Doklady Akademii Nauk},
     pages = {269--272},
     publisher = {mathdoc},
     volume = {234},
     number = {2},
     year = {1977},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1977_234_2_a1/}
}