@article{AL_1974_13_6_a3,
     author = {I. A. Lavrov},
     title = {Certain properties of retracts of {Post} numerations},
     journal = {Algebra i logika},
     pages = {662--675},
     publisher = {mathdoc},
     volume = {13},
     number = {6},
     year = {1974},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/AL_1974_13_6_a3/}
}