@article{AL_1989_28_4_a6,
     author = {S. V. Sizyi},
     title = {Critical theories of some classes of graphs and unary},
     journal = {Algebra i logika},
     pages = {454--462},
     year = {1989},
     volume = {28},
     number = {4},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/AL_1989_28_4_a6/}
}