@article{IVM_1977_8_a15,
     author = {A. B. Livchak},
     title = {Formula subsets of the ordered group of integers},
     journal = {Izvesti\^a vys\v{s}ih u\v{c}ebnyh zavedenij. Matematika},
     pages = {105--107},
     publisher = {mathdoc},
     number = {8},
     year = {1977},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/IVM_1977_8_a15/}
}